Should You ALWAYS Charge Your Home Battery Overnight?

[@GaryDoesSolar]

* NOTES SINCE PUBLICATION * 1. One benefit I failed to mention was that having a near-full battery most of the time really helps in the event of a power outage, which could have any time. 2. If you have an oversized array with a DC-coupled battery and your inverter supports charging of your battery with solar generation above the AC limit, it may be more financially beneficial NOT to charge your battery overnight when it's going to be sunny - instead charging it using a strategy that maximises that feature.

[@DerekHasted]

I live in a village where the power reaches us on overhead cables, before disappearing under the pavement for distribution. Having had 6 power cuts in 12 months, it's hard to put a price on the convenience of staying powered up, especially as I occasionally teach by video. I'm really pleased to be able to survive quite lengthy power cuts, keeping the frozen food cold in the summer and the frozen occupants warm in the winter.

[@RobAldred]

@@DerekHasted interesting, to contrast. Don't think i remember the last time we had a power cut up here in Chorley. 🤞

[@craigchamberlain]

Yeah I was going to mention your point 2. I have 6.8kWp of solar but can only export at around 4kW max so I try to start exporting early in the morning to ensure my batteries don't reach 100% until after the peak solar generation period has passed. This is becoming harder now as the year is progressing but I can still just about manage it. I still charge my batteries overnight but only to 20% or so, to ensure I have enough to power base loads until the sun starts shining strongly. I've not done the calculations but I'm pretty sure this will be financially better than charging to 100% and then exporting at 4kW max. Great video though, and will be the correct advice for most people. Keep up the good work. :)

[@clivewilliams3661]

@@DerekHasted We live in a village and experience power outages equally frequently but they mostly last for a very short time. The only inconvenience is having to reset the digital timeclocks A good few years ago the wrong sort of snow brought down the o/h lines and blew the sub-station. Power was restored to the perimeter of the village first and then go closer to us by the 3rd day. TBH it was an interesting distraction and being winter we didn't have a problem with our freezers. In fact, because we have a central heating solid fuel cooker we ended up entertaining friends and neighbours for much of the time as their gas boilers failed to function without power.

[@norfolkecokiwi]

@@craigchamberlain I was in the same boat as you with my oversized array, but managed to request a feature change on the inverter with the manufacturer and now I can select to "charge last" the battery. This means the consumption in the house gets the solar first, then it is exported up to my inverter limit (5K for me) before any additional goes into the battery. I believe this will only work for Hybrid (DC Coupled) inverters, so if you have one of these, it might be worth an email to the manufacturer to see if they are looking to implement that feature in the future.

[@simonm9923]

Another great video which really chimes with our situation. We fitted 9kW of solar (6kW peak E/W arrays), EV charger, solar diverter and two powerwalls (27kWh) in March 2020. Back then the aim was to self consume as much solar as possible as the tariffs at the time did not reward export. We exported less than 10% of our solar then but everything has changed with Octopus intelligent Go. We now charge the powerwalls, heat our water, charge cars etc. overnight and export ‘everything’ we generate while running the house on the imported overnight energy in the powerwalls. As of today we have exported over 70% of our generation ytd and expect to be net zero electricity cost for the year including two plug in cars and an ASHP. I don’t expect this tariff to remain unchanged (too good to be true?) but it highlights the advantage of having a flexible system which can adapt to a volatile and rapidly evolving tariff environment.

[@GaryDoesSolar]

Wow - that's a great report, Simon, and an inspiration to others, I reckon! :-)

[@davedevonlad7402]

I have a smaller system 4kw sola 10kw batteries "Puredrive" but I literally thought the same. Intelligent made all the difference and I export a very good amount for a small system. I use approx 10kw a day but I export 25kw+ on really good days, I charge my batteries every night but they are usually only 40-60% empty.

[@jameswestgate416]

Good to know I got it right using much simpler modelling spreadsheet, but also good to know your about your model too Gary. I think it’s fabulous that Octopus give a high enough export tariff that it pays you to charge overnight and export in the day. They are actively helping to balance the grid in this way.

[@GaryDoesSolar]

Thanks James - and I agree: Octopus Energy is really opening up the market for the consumer 👍🏻😀

[@davedevonlad7402]

I do this as well with octopus, charge up my batteries overnight at 7.5p per kw and the sun tops it up in the early morning and as soon as it reaches full 30 mins to 60 mins later it exports for around 8-9 hours for 15p per kW

[@magicgsuk6312]

I’ve not got an EV so cost me 15p. Eon have got a tariff that does cheap off peak charging that doesn’t require an EV.

[@johnpanunto183]

Thanks Gary, good video. I'm in Canada and just finished installing my solar system and that's my exact plan. One other benefit with a full battery at night is that you will virtually always be ready with a full, or close to full charge if the grid goes down.

[@GaryDoesSolar]

Hi John - you're most welcome - glad you found the video useful. Great point about supply outages as well - I completely missed to make that point in the video! I'll add a pinned comment to that effect - thanks! :-)

[@dreamz743]

+1 came here to say the same, having recently had an AC coupled battery installed

[@NathanJones-cq1dz]

I love your vidoes Gary, learning so much before my install takes place. I had been considering a second battery to my system to benefit from a very good 12 month SEG agreement of 40p. What I am now calculating is not purchasing a second 9.5kwh battery but instead using the 12:00 to 07:00 off peak period to fully charge, discharge and then recharge to 100% at an inport rate of 6.9p and an export rate of 40p. My 7.4kwp solar system to do it's thing and export throughout the day.

[@GaryDoesSolar]

Hi Nathan, thanks for your kind words! It's really good to model these strategies with utilities like Solarazma Suite. Please message me on Patreon if you'd like assistance with that.

[@Jaw0lf]

For me a fully charged battery means more export and since Octopus upped their export payment to 15p is incredible. Paying 7.5p overnight is a win win. Also it is nice to know we have some cover if there are any power cuts.

[@GaryDoesSolar]

Totally agree! 👍🏻

[@davew786]

Thanks Gary. I always charge the battery overnight. I’m currently on Agile with a small PV/battery system. My last few bills have an average import rate of 12p, so Agile is working well for me. The only thing I might manually do is to inhibit battery discharge during the late morning/afternoon until the 16:00 import peak starts. I do this particularly when the daytime and overnight import rates are similar (like in the last week). However I think I’ll do some calculations to see if the other tariffs are better in the summer. Keep up the great work!

[@GaryDoesSolar]

Thanks for the info, Dave. I like your strategy. Right now, I’m doing a bit of analysis for those with oversized arrays and a DC-Coupled battery… An interesting scenario to work out the best charging strategy 😳

[@redshift3]

An additional wrinkle with IOG. You could force discharge your battery just before the off-peak import period (I do this 10:30-01:30 to minimise the risk of fully emptying the battery during the peak period). This would further increase your overall income at the expense of greater battery cycles (but we bought our batteryies to put them to work) Similarly, on flux, force discharging your battery during the peak period can bring additional overall income

[@GaryDoesSolar]

Great idea for IOG! And agreed on Flux, which I cover in detail here: kzbin.info/www/bejne/mnjTpIFuYpZ5rpYsi=AVtkrMC1ljwqA056

[@michaelmcgoldrick78]

In Ireland we have some tariffs where we can import as low as 5 cents per kwh and export at 25 cents per kwh. Its only a 3 hours off peak window so that creates challenges depending on battery charge rate. I always charge each night regardless of solar forecast. I have an automation in home assistant which runs at midnight. It checks if the battery SOC if above 40% and the solar forecast is above 5kwh the next day and if it is it dumps it for 1 hour which works out about 3.6kwh export. From about March onwards this has been working well for me.. start most days with already having exported 3.6kwh... there were some gotchas - if i had the car plugged in or the eddi solar diverter set to 'on' the export would go into the car (if plugged in) or hot water. I've automation on these which switch them on at 2am and off at 5am.. (my tariff window) I have 13.6 kwh usable battery and 7.1 ish kwp.. seems to be very similar to Tim from Tim and Kats green walk channel.

[@GaryDoesSolar]

Hi Michael, a great strategy! And I do hear from time to time about Eddi's, batteries and EV chargers not playing nicely!

[@alicat398]

Automation sounds great. You should do a video on that!

[@Leopold5100]

WOW, what fantastic information, thanks

[@GaryDoesSolar]

Thanks for the great feedback! 😀🙏

[@colinfieldgate4719]

If using Octopus Intelligent Flux you can generally get the best results by charging to 100% just before the peak period (using your modelling).

[@GaryDoesSolar]

And I think Octopus Energy aim to do just that with their remote control software...

[@bz4743]

Definitely my strategy in winter with Intelligent Octopus Go, but in summer I want to limit my DC charge due to an oversized system

[@GaryDoesSolar]

Sounds good!

[@GarethJones-dk9yp]

Good video. I've got a very complex node red flow controlling my ESS which does a similar thing to what your software does. On intelligent Octopus Go. I look at the next day solar irradiance, battery SOC, and predicted consumption. Then at 23:30 I adjust the charge current for the 6 hours and it works really well. Keeping the charge current as low as possible allow the system to.run at maximum efficiency. It's rare that I have off grid days and find it always charges at night. I'm either running of cheap off peak or free energy from solar. 😊

[@GaryDoesSolar]

That's just brilliant, Gareth! :-)

[@johntudor2178]

I have to manually control charge and discharge as, now with decent irradiation I try to deplete my 2 SolarEdge energy banks to allow them to take some charge from ordinarily clipped power. My 10 kWp array can generate 9kW and with a 6kW inverter 3kW would be wasted. It’s tricky but satisfying when you get it right. Very informative video await the next in series

[@GaryDoesSolar]

Thanks for this, John. Yeah, a few people have mentioned about clipping. Personally, I'm not sure if changes things all that much, but you're right - it's the fun of trying to get the very best out of your system! :-)

[@TheRonskiman]

I've been on Flux for a year now, and have been doing this all that time, currently off peak import is 15.175p and day export rate is 15.652p. There will be some efficiency losses, but the cost is so small its not worth worrying about. I charge for exactly the reasons stated, no need to worry about what the weather is doing. I have an 8kW inverter and 29 kWh of batteries, so come 4pm I force discharge to 45% SOC charge, which gains me quite a bit every day - currently exporting at 7kW, DNO approval to 11.68kW as I also have another AC connected inverter.

[@GaryDoesSolar]

Thanks for sharing your experience with this - great to hear! :-)

[@stevendigby6125]

My system is like yours is in the flux - exporting seems to work automatically. How do you use force charge it between four and seven ?

[@TheRonskiman]

@@stevendigby6125 Between 4pm and 7pm I force discharge, not sure if you mistyped or misread. I have a Victron system, and I wrote my own Node Red code to monitor battery load & SOC, and use that to set what rate I want to force discharge at. Most system have the ability to do it, but its not always straight forward.

[@stockdale1]

Another great video, if you have export at double than import it's a no-brainer. Now into spring I'm exporting by 8am. Best move I made was oversizing the array to the inverter.

[@GaryDoesSolar]

Great stuff - thanks for sharing!

[@colingoode3702]

Another good one Gary. I recently switched to Octopus Intelligent Go I have now changed my charging routine. As you suggested, I now charge my batteries overnight between 11.30pm & 5.30am without exception. I also charge my car & run any appliances overnight that have a delay timer all on the 7.5p/kWh night rate tariff. In addition, between 11.30 & 5.30am I prevent / pause my battery from discharging (GE Portal setting). This prevents the car, or anything else, from draining the battery overnight & ensures I start the next day with the highest possible battery SOC. If the sun is out next day then I'll be exporting to the grid & earning 15p/kWh as early as 7am & for most of the day (ESE array). If there's no sun then I run my house from the 19kWh of stored battery energy plus whatever solar is available throughout the day. I'm already seeing a dramatic reduction in our monthly energy bill by way of generation credits & best of all I don't have to watch the weather any more like a Met Office geek!! 🌧🌞

[@GaryDoesSolar]

That's brilliant, Colin - your comment is exactly why I released this video, so that others can achieve the same! :-)

[@tamsineh]

Don't think you need to pause the battery from discharge during off peak if it is set to charge....just a thought

[@colingoode3702]

@@tamsineh Yes, but if the battery finishes charging before the car then the car sucks all the juice out of the battery for the rest of the night or until it finishes charging. My car charger & inverter are different makes (ME Zappi & GE 3.6kW Hybrid) so they don't talk to each other. Pausing the battery discharge for the night rate time period is the simplest solution I've found to what is a fairly common problem.

[@davedevonlad7402]

@@colingoode3702 I have a zappi and different batteries "Puredrive" and a Solis inverter, my car doesn't discharge my batteries at all as there is a way to set it up to charge only from solar and the 11:30pm to 5:30am on octopus intelligent. I can charge my batteries while charging my car and run my overnight appliances all at the same time during this period. If your car needs more juice than the six hours octopus can schedule a charge out of hours but even for the lower price you would get during the six off peak hours. So it is possible as I looked it up and asked my zappi installer to do it this way. You need to change some settings on the zappi but it's pretty easy to find out how to do this. There is a KZbin video on this but I can't remember what it is called.

[@tamsineh]

Oh yes of course, I have a zappi too. If my car charging extends past 0530hrs, I usually extend the battery charge too as octopus intel go are giving me extra charge hours. I can't really get on with the desk top version of the give energy app so I stick to what I can do in the app. version.

[@MrLeecavturbo]

Hi Gary while I commented earlier this is my current strategy I’ve just discovered why you maybe wouldn’t when guaranteed sun. My inverter will export its maximum kw ( ac ) and charge the battery at the same time if you have solar PV over the rating of your inverter ( not all inverters may do so ) but my 5kw inverter can export 5kw and charge at 5kw simultaneously. I have 7.5kwp so there is a case for charging in the day so I wouldn’t be impacting/reducing any export 👍👍👍👍

[@GaryDoesSolar]

Thanks for sharing this, and in fact I added a pinned comment to the video now, as there is a clear case not to always charge if all of the following is true: 1. Your array is larger than your inverter output 2. Your home battery is DC Coupled 3. Your battery charging (including charge rate) is carefully managed 4. The method you use to do 3 (automated or otherwise) is foolproof

[@johnh9449]

Very good Gary. Something I considered a while ago and realised whatever you put into your battery in excess of what you need gets exported and you get paid back at twice the rate on Octopus Intelligent Go for example. However, have you considered what happens when the battery reaches 100%, say two hours into the six hour charge period and then you run for four hours supplying the household load from grid which is possibly significant such as a heat pump? That four hour period is a grid draw and expense that isn't recovered by export. Arguably as soon as the battery reaches 100% it would be better to stop charging and start to consume battery charge. Even better would be to delay the charging so the battery reaches 100% as late as possible making export happen as early as possible. I must admit I've not modeled this yet as I've only just considered it. It's the long six hour off peak on Octopus Intelligent Go as opposed to standard Go, where my battery struggled to reach 100% over most of winter, that's highlighted the issue. I was wondering if it's better to stay on Intelligent Go or switch to Flux over summer as I had presumed was the best thing to do. Flux has a better export rate between 4pm and 7pm but doesn't have as cheap an overnight import and for only half the time. However if you can't charge the battery with the extra cheap hours because it's already full that dead time won't turn into earlier export so perhaps Flux regains the advantage. For the moment I've set my Intelligent Go charge time to three hours whilst I think about it.

[@GaryDoesSolar]

Thanks John - yeah, at least if the battery hits 100% early during the off-peak period, any grid draw from the home is still at the cheap rate. I'm on Agile and I use remote battery management software called MyEnergyOptimiser. What it does is stop the battery from charging or discharging when it reaches 100% until the import price rises above a certain level.

[@DerekHasted]

Another clear video, thank you! What I don't see in your modelling is the losses which mean that when you put 10kWh into a battery, you'll get less coming back out. For our installation, the installer estimated the total round-trip loss occasioned by the battery and the two trips through the inverter to charge and discharge as about 10% in total. I've no idea whether I'm seeing that sort of loss or not, but any loss means that paying to put charge into the battery and then selling that electricity back to the grid as soon as the sun comes up is not quite as profitable as just looking at the import and export rates suggest... I'm not suggesting that charging overnight is a bad idea, I'm just noting that whether you charge your battery to 100% on the grid, or on the solar, you'll lose quite a bit of electricity on the round-trip through the battery. Then again, I'm coming to the conclusion that absolutely nothing in this game is quite what it first seems! All the best, Gary...

[@GaryDoesSolar]

Hi Derek, thanks for your kind words. Yeah, it's always difficult to model real-world scenarios with software, but I do believe what I've created is good enough for reasonable conclusions to be drawn. You'll be pleased to know that the utility does take into account round-trip losses (configurable in the settings)...

[@st200ol]

Another night/day of negative prices. I don’t have batteries but I’ve read some people charge batteries using solar during the day, dump it back to the grid and then then charge again when the price is negative. Repeat as required

[@GaryDoesSolar]

Yeah, I guess the trick is to be as flexible as possible to take advantage of all these opportunities ❤️

[@stevegame3000]

Great video. I have just had my export tariff set up so can get payment for export at last. My problem with overnight charging of my battery is that my array peaks at 5kW when the sun shines but my DNO restricts export to 3.6kW. I guess I would only charge the battery overnight when the forecast is cloudy. Maybe even restrict the battery charge rate during the day to lengthen the window when some of the generation was going to battery (when it’s sunny)

[@GaryDoesSolar]

Thanks, and worth a shot, certainly. The modelling tool allows you to set the charge/discharge rates if you wanted to perform some analysis in advance.

[@PaulLandregan]

Nice video. One scenario to consider. Dump some or all remaining power at night. For 15p. Then put it back in for 7.5p. Downside is battery wear

[@GaryDoesSolar]

Thanks Paul - and agreed, for IOG, most definitely! And true about more cycles but I know my GivEnergy batteries can take it! 😀👍🏻

[@aag4utube]

​​@@GaryDoesSolarwhat are your thoughts about keeping the battery at a 100% for a longer period. I believe this is generally discouraged in EVs. Would there be any long term impact of keeping the battery close to a 100%

[@GaryDoesSolar]

@@aag4utube That's an interesting question, and one I'd need to check on. Looking at the SOC profiles in the utility, the battery does stay at 100% for a significant part of the day when sunny. I'll ask a couple of people who understand battery tech better than I...

[@twelvebears1971]

We are currently on Flux and about to switch to Intelligent Go next week when our EV arrives. I had been trying to keep some space in the battery and adjusting charging rate to avoid clipping during the day as we have a 5.5kW inverter and 6.5kW of PV, but with the UK weather being what it is, it’s quite different to judge. I think I’m going to revert to the fully charging overnight strategy.

[@GaryDoesSolar]

Yeah, I think you'll like the results of doing that - especially the increased revenue from exports! Hope all goes well with the arrival of the EV :-)

[@davedevonlad7402]

This video really makes a lot of sense. I am on octopus intelligence with my system consisting of 4kw sola 10kw Puredrive batteries a 5kw inverter and an ev, i charge up every night but as he says in the video my batteries are usually 40-60% full by the time it needs charging so i usually don't need much overnight except in the winter when my batteries very occasionally runs low during the day and we use the grid for a hour or two in the late evening. I export a good amount for a small system and it really has cut my electric bill by much more than half even with an ev. I make sure i shift my washing machine and dishwasher to the low night time tariff to get the benefits of 7.5p per kw. And when i get an ashp and water tank i will be doing the same. The information in this video is accurate as i came to similar conclusions months ago while working out if was going to be viable.

[@GaryDoesSolar]

Thanks David :-)

[@davedevonlad7402]

@@GaryDoesSolar Just a thought, I would really like to know what other owners of home storage systems "State Of Health" of their batteries are after a year to say five or ten years and what brands hold a good S.O.H if charged and discharged once a day. It would make an interesting comparison. Are we getting our money's worth!

[@gopikrishnayogarajah]

Nice video thank . Only thing for people like me who have restriction on how much we can export , it is not that straightforward . The MPTT's will throttle down if production is too much to match export limit.

[@GaryDoesSolar]

Thanks - and yeah, an export limit is certainly problematic for strategies like this. Self-consumption becomes the priority then, I guess?

[@gopikrishnayogarajah]

@@GaryDoesSolar I just need to limit peak export kW .. Keep the batteries sort of half charged for absorption during peak production that exceeds limit and just spread the export out. I am on octopus flux. I have a Victron inverter and trying out their Dynamic ESS feature that does this ...results are good but its new and makes some small mistakes here and there.

[@MattyFreedom]

Yep I charge regardless with flux. No faffing around and I know I have a full battery most of the time in case I need the emergency power too. It’s a no brainer.

[@MattyFreedom]

Though I do dump during expensive time, which keeping the battery full also helps with.

[@scwebb]

Me too.

[@GaryDoesSolar]

A sound strategy! Thanks for sharing, Matty :-)

[@hufartd]

What size battery do you have and what level do you dump to?

[@MattyFreedom]

@@hufartd 10kwh, dump down to 40% which leaves me enough for the evening most of the time. I’m nicely up the majority of days this time of year. Pays the gas when it’s not cold too.

[@Joshie120]

Charge my Soalr Battery every night (11.30pm-5.30am) + any extra IO Slots (I've got HA Running) and then i export at 15p per kwh, but i buy it at offpeak at 7p.. making me negative £20 per month. I also sometimes force discharge my battery at 15p to then refill it at 7p - but this exclude battery wear etc.

[@GaryDoesSolar]

Sounds like you’ve got a pretty good strategy there 😀👍🏻

[@stuartburns8657]

Very interesting. I will admit i've always set to solar only historically, but this might make me change tact

[@GaryDoesSolar]

Definitely worth a shot, Stuart, to see the effect! :-)

[@9111logic]

🙏 Thank you for your analysis, however, no one seems to discuss situations where the solar system is not tied to the grid but instead switched on or off if and when required. The Octopus website is probably one of the worst for information as it also does not mention if the inverter needs to be linked to the grind to obtain certain tariffs. I sincerely hope that someone will realise that not everyone is grid-tied and will cater to those who have gone to great expense to build an excellent PV Micro Grid in order to alleviate the grid load but do not want to be fully connected and be at their mercy also for genuine technical reasons.

[@bloodynorahvan2203]

I came to the same conclusion as you for Intelligent Go. However it still irks me to export more of my solar, instead using overnight, which is often less clean than the solar. Still, 15p export vs 7.5p import is worth having. I wonder if anybody has tried force exporting their battery every night at 23:30 to see if this also generates 15p income?

[@GaryDoesSolar]

Yeah, if the export rate is fixed, then you'll get that rate whenever you export. I agree, that doesn't seem right to me, but it is what it is...

[@twelvebears1971]

We’re about to switch to Intelligent Go and would have spare capacity to force discharge and then fully charge during the extended off-peak period. I’d still like to contribute to the grid at the most helpful time so I’m still planning to do this between 4-7pm as this is typically the most expensive or dirtiest period for the grid.

[@W2APS]

Another fantastic informative video. I regularly forward them on to friends and family who are either considering PV and battery systems or really should.

[@GaryDoesSolar]

Thank you for this great feedback! 😀 And thank you also for spreading the word 👍🏻

[@alanrobins]

Hi I am with flux and charge the battery every night Usually by 0930 mid April my battery is fully charged (if sun out ) rest of the day export It’s a no brained the export rate and night off peak are virtually the same so with earlier 100% getting max return during the peak sun time

[@GaryDoesSolar]

Great to hear, Alan! :-)

[@alanrobins]

Hi Gary I have just looked at my actual figure for April to date I live in Norfolk with variable amounts of cloud Import 65.75 kWh £10.42 including vat Export 299.65. £46.47 Own use 140.78 kWh Octopus have just credited me £450 I went into November over£600 in credit and I still am in credit now I am self sufficient I have not paid anything for electric in the last 18 months

[@GaryDoesSolar]

@@alanrobins Ok, that's marvellous! 😃

[@MarksElectricLife]

If you're on a wholesale plan like Amber in Australia you get charged for daytime exports so it makes no sense to fill your battery at night and then get "taxed" for exporting in the daytime.

[@twelvebears1971]

Fortunately the UK is never likely to see so much domestic solar generation that charging exports becomes necessary, so as with everything, people have different circumstances.

[@GaryDoesSolar]

That;'s a fair point, Mark. And the strategies for tariffs in many parts of the Southern Hemisphere have to managed differently. I talk about this here: kzbin.info/www/bejne/jaHOfYtmfLmGe5Y

[@postiemania]

I am on Amber and sometimes I get charged for exports but most days I can get $0.50AUD. But Amber has cheap power as low as two cents per kWh. My average price is 20 cents per kWh. Amber is great I can see my daily cost and use. Really good if you have batteries to ride out the peak prices. I have solar and batteries and my electricity costs are $2.00AUD.

[@twelvebears1971]

@@postiemania and presumably you can set your inverter not to export back to grid? If export is so poorly paid/charged? Or is having export enabled a condition of the cheap import prices? Clearly the solar tariff market is vastly different to the UK.

[@JohnThomas-ey1hx]

Maths don't lie - good video. How does this model pan out with Agile charging to 100% with a fixed 15p export? Guessing some days will be better/worse than others depending on the varying slot charge price used.

[@GaryDoesSolar]

Thanks John - yeah, I didn't include Agile in the analysis as most people will have automated battery management running with that anyway (e.g. Home Assistant, Predbat or MyEO) and that management should manage the charging and discharging for best results anyway...

[@serraios1989]

Thanks Gary. You have put a lot of hard work into your channel. If battery loses are factored in, then at the current flux rates the profit is only 1.8p/kwh-exported and for the IOG 2.5p/kwh-exported. I have a GE 8.2kwh battery. You will get very interesting results if you ever test the efficiency of your battery. Certainly different to the app readings.

[@GaryDoesSolar]

Thanks, yeah - it does take it out of me, producing these videos - but I really love it that they're helping people out (or at least getting them to think about things more) :-) Good point about battery losses - and I do account for these in the utility... In real life, I'm hearing stories of 20-30% losses in the battery. That doesn't feel right to me, given the manufacturer statements of around 10%...

[@serraios1989]

At full charge/discharge rate the battery loses are about 30%

[@Th3Dean]

Great video. I wonder if the next stage is for the app to calculate the best possible tariff given location, array & battery size etc

[@GaryDoesSolar]

Thanks and I like your thinking. So at the moment, it's quite a manual process to set up the tariffs, but I'm working on a module where you can set up and name multiple tariffs. Then, I'm working on another module that provides an annual view for a given tariff, not just a daily view. A lot of work to do, but I'm heading there slowly :-)

[@norfolkecokiwi]

Really interesting video again Gary. I was wondering if your utility takes into account oversized hybrid (DC battery coupled) inverters. I have 7.38kW of solar running on a 5kW hybrid inverter. I do use weather compensation to determine how much to charge my batteries overnight moving away from fixed charging in order to maximize the amount of generation. What I had noticed with the fixed charging times was that by about 11am the batteries were full and my solar generation was "clipped" to the 5kW inverting capacity of the inverter. Being that I have a DC coupled battery system, then normally what would happen is any solar generation above 5kw could be put into the battery. I therefore have several options open to me. The first is to use weather compensation to not charge as much or I could also restrict the charging current to the battery over the day (sending any excess generation to the grid for a nice export payout). In either scenario however if my battery is full, even though the solar panels have the capacity to generate more, they'll be clipped to the 5kW once my battery is full. If you don't already factor this in, it would be an interesting case study (and more that happy to share my actual solar generation figures if that helps).

[@DarkS1m]

I have the exact same setup and just got my export approved today! I was also wondering about the effect of clipping losses. Today I was peaking at 6.5kW generation, with 5.3kW going to the inverter and the rest to the battery. It filled up by noon, and clipped to 5.3kW (5kW output with inverter losses), but had I charged it fully overnight, I would have lost that extra couple of hours of free sun. My gut says it's safer to fill up if it's going to be cloudy, but a lot depends on tariff. Might be overthinking this, but unfortunately Solarazma Suite doesn't model this hybrid functionality (yet...)

[@DarkS1m]

Tried a new tactic today by limiting the charge rate until the solar generation exceeded 5kW. Worked much better than filling up in the morning and then losing all the midday peak to clipping. I reached a new maximum of 7.1kW generation! The downside to this method is it's quite weather dependent, and has to be done manually on the GE app, as there's no advanced scheduling options yet. Also if there were a power cut, the battery would be in a lower SoC - although I'm told it does still fill the battery from solar if you have an EPS circuit.

[@norfolkecokiwi]

@@DarkS1m This was my point exactly. If you are fortunate enough to have a system that can take account of weather compensation (kzbin.info/www/bejne/pJivknqgmZuCf8k), then it is possible to maximise the overcapacity of your solar whilst still ensuring you have sufficient power available in the battery for those cloudy days. If you don't have weather compensation available on your battery inverter, then you may have the option to use "Home Assistant" to implement it (kzbin.info/www/bejne/nHeToJeEjbmrapo).

[@GaryDoesSolar]

Thanks for sharing this. I must admit, in the video I didn't properly consider an oversized array, and on some of the solar forums I am a member of, there were some comments about the same thing. For my own installation (7kWp array with a 5kW inverter and 2x9.5kWh DC Coupled batteries) I figured that I could export an additional 7kWh by tight management of the battery charging in the ways you discuss above - which at 15p is an extra £1 on every fully sunny day - not bad!

[@norfolkecokiwi]

@@GaryDoesSolar Further to this discussion, I had requested a feature update to the firmware of my inverter (Luxpowertek LXP5K) and they have just recently applied that feature. This allows me to set a charge priority for the battery where I can now select to "charge last" the battery. This means, any solar first goes to serve the household consumption, then any additional solar gets immediately exported and only when my maximum inverter output of 5K is reached will it then start charging my battery up to the solar array size of 8kW. This when coupled with the "weather compensation" to set the battery charge level appropriate for the day means I am keeping the battery charge level well within the 20% - 80% SOC (which is good for the batteries) and I am not wasting any solar energy during the day. Happy days. I hope other inverter manufacturers think of adding weather compensation and charge last as a standard feature as this would help many of us who have oversized arrays benefit during those sunny days/months. It is likely this could also be implemented with Home Assistant too.

[@jatindersehmbi6239]

Hello Gary Loving your channel. I have one question: Most of the tariffs you mention require an EV to sign up with them. The switch to Intelligent Octopus Go or even Octopus Go require a successful test charge to be eligible......I don't have an EV and probably will not get one. Are there any other tariff options available that you can recommend? Keep up the excellent work.

[@GaryDoesSolar]

Hi Jatinder, thanks for your very kind words 😀 Here are a selection of videos covering Octopus tariffs I really like where you don’t need to have an EV: Octopus Flux: kzbin.info/www/bejne/r2nHYpyno82om80 Agile Octopus: kzbin.info/www/bejne/g5O4dXqYo617eKc Intelligent Octopus Flux: kzbin.info/www/bejne/q5LPqaeCgaaqmcU Enjoy!

[@71brp84]

Great video again Gary but, theres no mention of clipping. How does the utility deal with this, if at all?

[@GaryDoesSolar]

Thanks. Yeah, the utility can manage clipping. My own array is oversized, so I tried the three tariffs with that, and actually it didn't make a lot of difference.

[@71brp84]

@@GaryDoesSolar that's interesting to hear. I've got 7.6kWp EW solar and 5kW Giv hybrid on IOG but, you're saying that sacrificing peak generation doesn't really have a significant impact the return?

[@GaryDoesSolar]

With the quick modelling I did on my own installation, it didn’t affect things very much at all. Remember, that on sunny days, your battery will get to 100% by mid morning so can’t really take advantage of the peak solar stepping noon… You’d have to be continually dumping your battery to the grid in order to keep enough headroom. Just my view though…

[@Dory222]

It's worth noting that you can import and export electricity from different providers. I import from Octopus Energy and export to Scottish Power.

[@GaryDoesSolar]

Yeah - do you find it's advantageous?

[@Dory222]

@@GaryDoesSolar when I was on Octopus Go I was exporting to Scottish Power at 12p/kWh rather than the 8p Octopus would have paid me. I've just switched to Octopus Agile for import, so I'll need to decide whether the hassle of switching my export to Octopus would be worth the extra 3p I'd get.

[@IanDonald-b2x]

Now that from October 1st Octopus are reducing the Flux daytime export rate to less than the off peak import rate, will it make more sense in the spring to charge the battery from solar? I started charging mine off peak every night after seeing your video but I am now thinking that the new rates will make it uneconomic to do so when the sun shines next year.

[@GaryDoesSolar]

Always worth running scenarios through a model like Solarazma. A reducing export rate changes things 👍🏻

[@garryhellings5311]

Hiya, Agile for me, I have 4 KW panels and 12 KW batteries. I have my lux hybrid inverter set to automatically charge overnight when the 30 min segments are at lowest prices. I always take advantage of the negative pricing plunges and saving sessions. I guess going by your excellent video I have been doing it right from day one, my roof is south facing which really helps my generating. The fly in the ointment with all of this is the standing charges, do you think octopus will better the 15p fixed export this year?

[@GaryDoesSolar]

Hi Garry - yeah, sounds like you’re doing all the right things 👍🏻 I agree, standing charges are bordering on criminality. With electricity prices coming down of late, I don’t think export rates will rise any more… but never say never! 😀

[@MrKlawUK]

you could go a step further with IO and force discharge the battery just before 23:30 and then fully charge. This would increase the cycles slightly but you’d gain a little more too much

[@GaryDoesSolar]

Interesting idea - I hadn't thought of that! I should do some modelling...

[@barrysnelson4404]

We don't get paid for export - there is no export meter..We get paid for 50% of what the generation meter says (regardless of what we used and actually exported). We charge from solar as much as we possibly can.

[@GaryDoesSolar]

Hi Barry, yeah being on the UK FiT scheme is a pretty good place to be! :-)

[@keithfarrow5839]

I get paid 15p for export. Any time import is below 10p it makes sense to charge the batteries.

[@GaryDoesSolar]

Can’t argue with that 👍🏻

[@philip_james]

Only thing is my 3.6kw hybrid inverter doesn't clip the solar when it's charging the battery so I can actually generate more if I don't charge the battery. For example if my battery is at 100% the solar is clipped and my max output is 3.6kw. If however it is charging my battery I can see a solar generation of 5.2kw until the battery is full so I limit the maximum charge rate of the battery to stop the battery filling up too quickly. Just another thing to consider 😁

[@GaryDoesSolar]

Great point, Philip - and a few people have mentioned it. On a sunny day, it's REALLY hard to avoid your battery reaching 100% before mid morning though - I like your idea of limiting the charge rate outside of the off-peak period!

[@tristanblaine8544]

Another very useful video, thanks. I spent some weeks deliberating what to do and this backs ups my findings. I'm on Flux, with a 5.8kW south facing array and GivEnergy battery and inverter. Was charging to 80%, the risk of pulling in at peak in the evening put me off, so charge to 100% now.

[@GaryDoesSolar]

You're very welcome, Tristan - hope the new strategy works well for you...

[@geoffreycoan]

Thanks Gary, you will doubtless get lots of comments about specifics of the modelling scenario. For Intelligent Go, I agree, the overnight import rate is so much better than the export rate that it does make it worthwhile to import overnight. For Go and Flux, I’m not so sure. For Flux in particular by the time ~15% conversion losses are included I think you’re definitely better off not charging overnight, or if you want some contingency against poor solar, only do a partial charge overnight. In fact partial or no charge has the additional advantage of reducing the impact of solar generation clipping as you can trickle feed the battery during the day from solar to avoid generation or export limit clipping occurring. All good fun and a model like this makes it easier for people to understand the trade-off’s

[@GaryDoesSolar]

You're most welcome, Geoffrey. And you're right, trying to model the real world is always a challenge. Having spent thousands of hours on it, and with the feedback from hundreds of people, I do believe my modelling software is reasonably accurate - enough at least to draw broad conclusions. Like you say though - it's good fun and if it gets people thinking then that's a win! :-)

[@MrWobling]

Is there a way to avoid self consumption of solar during the day, perhaps by steadily discharging the battery during the day, increasing as needed to cover consumption peaks and exporting an excess? This would avoid having the battery sit at 100% most of the time and avoid needlessly recharging the battery during the day, in the event it falls below 100% (as long as it discharges along an acceptable "flight path", so you don't run out while cooking dinner)? I can't seem to find a combination of settings to do this with my GivEnergy battery, but wondered if I could automate via Home Assistant.

[@GaryDoesSolar]

Hi Andrew, I don't have an answer to that myself, but perhaps others do...

[@rodden1953]

Thanks ive been asking this question for a long time as i live alone with a Powerwall so i stayed on the standard tariff . But will i still be able to keep my FIT payments on top ?

[@davidvincent5244]

Your FITs will remain with the original supplier unless you choose to move it to Octopus. The Generation (off roof PV )will continue. You will sacrifice the FITs 50% export. But gain the 15p from Octopus Export tariff. You also can move the FITs Generation to Octopus. Which keeps it all in one place. The thing to remember is your Import, Generation (PV) and Export (PV) are separate contracts. So, Generation is with OVO and my Export and import is with Octopus 🐙😊

[@rodden1953]

@@davidvincent5244 Thanks i am with Octopus and i now get about 20p kwh so i would get about 25p if i moved to another tariff then ?

[@GaryDoesSolar]

Best not to touch your FiT I reckon. Here's a link to a resource on the scheme and making changes to it that might help: facebook.com/groups/2197329430289466/permalink/6080359505319753/

[@rodden1953]

@@GaryDoesSolar Thanks Gary i thought i was doing the right thing as im single i get about £500 a year in FITs and for 6 months im basically off grid and as im retired i can use the Zappi any time i need it for the car . PS im locked out of Facebook

[@rodden1953]

@@GaryDoesSolar Hi Garry this makes sence but im going all electric soon with Air to Air do you think i should change now ?( im locked out of Facebook ATM )

[@dbas2]

Thanks Gary. Another interesting viewpoint to consider. Many battery systems allow the limiting of the soc from the grid to below 100%. However, not so with solar. So even if I limit my import to recharge, the battery still fills to 100% from solar before export occurs which is a little annoying. Batteries don’t operate well as they approach 100% charge hence we are often told to limit the recharging cycle between 20-80% to aid battery health and stop degradation. What is your view on this and can your modelling accommodate such scenarios?

[@GaryDoesSolar]

Thanks David, and you raise a good point. Whilst the model can limit force charging to a certain percentage, it doesn't limit charging from solar - and I've not seen any equipment (yet) that can do that. But I've observed from my own installation, that as the battery heads towards 100%, the charging rate slows down (as you say) - but that means the remaining solar is immediately exported to the grid (assuming the home doesn't require it).

[@dbas2]

@@GaryDoesSolar Thanks Gary. I’m not sure that I agree with your last point as energy is lost to heat and therefore ‘wasted’ at this level of battery capacity. I think it would be better if we could limit charging regardless of source.

[@RobAldred]

Hey Gary. Another super interesting topic. Do your calculations account for losses into and out of the battery? In North West, our regular flux export is only 0.05p more than the flux low import. Be interesting if the losses make it pointless to charge. I've been tweaking my home assistant setup and it's gotten pretty good at correctly deciding if to charge or not.

[@GaryDoesSolar]

Hi Rob, thanks - and yes, the utility takes round trip losses into account 👍🏻

[@RobAldred]

@@GaryDoesSolar nice i shall give it a whirl

[@MK_Maestro.1]

Great idea. Q: AC coupled inverter - does the AC from panels go 'straight thru' to the grid without converting twice (AC into battery as DC then out as DC into AC) thus saves c6-8% generated power?

[@GaryDoesSolar]

This doesn’t make sense. Panels don’t generate AC.

[@MK_Maestro.1]

@@GaryDoesSolar No they clearly don't , unless they have a micro-inverter attached to feed AC into an AC coupled inverter..... Ne'er mind Gary as I have found the answer elsewhere. Sorry to have confused you.

[@GaryDoesSolar]

No worries. Glad you found the answer 👍🏻

[@karlyau655]

What about if your array is oversized? I have 6kwp panels, but can only export 5kwh (and typically use 500wh through the day). Therefore on a sunny day, if my battery is 100%, I use 500wh, export 5kwh, and am clipped 500wh. I try and keep my battery at 80% through afternoon, then allow it to charge to 100% just before 4pm, when I export at peak rate. But that’s all manual and not really sustainable. Is there any strategy for utilising all of the power? Is there any modelling tool which can take account of this ‘loss’? (Am I just being too tight?)

[@GaryDoesSolar]

Hi there, I think you might like this utility I developed then: garydoessolar.com/solarazma_pro_intro/

[@michaelblackmore883]

Hi Gary, one point you didn't include in your " better for the environment" argument is that most of the energy from the grid overnight will be generated by burning gas. If this is valid it will get less environmentally beneficial as our (UK) nuclear generating capacity declines as existing power stations are decommissioned and the replacements (on past form) fall further behind predicted commissioning dates. Have I missed anything? Mike

[@GaryDoesSolar]

Hi Mike, you're right - a decreasing nuclear capability is certainly an issue, especially if the wind isn't blowing. I'll need to think about this. Of course, every day, more and more EVs are coming on stream, so there needs to be a solution of some kind...

[@peterjones6322]

I would say with low night time demand and wind and nuclear supplying the grid, the gas stations are more likely to be switched off. Plus Octopus state that they only sell electricity from renewable sources.

[@michaelblackmore883]

@@peterjones6322 Of course you are right about what Octopus buys. However everything that is generated from whatever source can't be separated once it flows into the grid so the "electricity" that enters your home is the same as from any supplier. Nuclear only supplies a very modest proportion of the output from the grid - regrettably - so unless it's a windy night gas is very likely to be providing a proportion of the load. The more people who use off peak the more likely it is that gas will be a significant contributor until more nuclear comes on stream to provide increased base load.

[@michaelblackmore883]

@@GaryDoesSolar A conundrum until HMG gets off the fence and commissions RR to get a few SMRs on stream to plug the gap until the "big ones" are working.

[@mark82421]

Gary, great video and analysis. My concern with charging the batteries overnight to full (I am on OIG) is that my 20kW pure drives with a sunny period never deplete, they are cycling between say 70% and 100% is this good for my PuredriveII's? not so sure, does the earned money offset the reduced SOH? any thoughts?

[@GaryDoesSolar]

Thanks Mark, and if you look at the chart in the utility, it would be the same SOC profile even without charging. Remember though, not every day will be sunny and so the battery SOC will drop right down on those days. I don’t see any issues long term other than normal battery wear 👍🏻

[@OwenWarnock]

Gary, at minute 6.35 on this very interesting video you say that charging your battery every night from the night rate has no impact on battery life becuase it is st5ill only one cycle of charge and discharge a day. However, I think that would only be true in the summer. In the winter, at breakfast time the battery will start to discharge as elecricity use picks up, because there will no solar input until it is light enough, so there will be some discahrge. Later, when the light gets stronger the battery will start to charge until sunset, at which point the battery will start to discharge again to meet evening electricity consumption. Then, in the night-rate period the battery will be charged again - so that is two cycles a day, not one. Can you model-in the impact of this on cost - i.e the reduced battery life?

[@GaryDoesSolar]

Remember that one charge cycle is going from 0% to 100% then down to 0% again. If you go from say 50% to 100% then down to 50%, back up to 100% and finally down to 50% again, that’s still only one charge cycle.

[@CiaranCalik]

In Ireland I can charge my 10 kw battery over night for 10 cent a Kw and sell the solar energy that would have been use to charge my battery when the sun is out for 21 cent. Sounds like a winner but because I export above the 400 euro export tax free earnings limit for micro generation. Battery charging overnight is not violable option, the 21 cent earnings per Kw taxed at 52% brings me back to the 10 cent I'm paying to charge over night plus I'd have to pay peak rates, if I import in the evening. Are PV profits taxable in the UK?

[@GaryDoesSolar]

Sounds great! In the UK, reading the Smart Export Guarantee (SEG) legislation, it looks like so long as your exports generation doesn’t exceed 120% of your import, it will be free of tax. Of course things could change in the future…

[@CaptainProton1]

I'm on Inteligent go linked to my EV but it says on the Octopus site that my export can only be £0.07 and not £0.15?

[@GaryDoesSolar]

So this webpage might answer. It says that Fixed Outgoing Octopus can be linked to Intelligent Octopus Go: octopus.energy/export-tariffs/ Now, for plain Octopus Go, unfortunately, they only offer Outgoing Lite, which is 8p/kWh

[@DW-hn8bk]

Hi Gary. I am downloading the energy data from Myenergi Zappi which provides in half hour periods the following data: Import, Export, Solar, Zappi, Self Consumption, and Total Property. We are in the process of having a PowerWall 3 installed. Please can you advise whether this data can be imported into your model to analyse our usage. We have a Tesla Model 3 which can also be used to export to the grid using Intelligent Octopus Go which we will transfer onto when we have the battery installed. We are currently on Flexible Octopus with FIT through another green energy company as we were originally with Bulb who did not have FIT arrangements when we started with them. Many thanks for your advice.

[@GaryDoesSolar]

So my modelling tool is purely theoretical, using a typical Daily usage profile as it’s input. There are many apps available though for those on Octopus energy tariffs, where you can input all of your actual usage data then perform comparisons.

[@RichardEricCollins]

I'm on octopus. My system has 12kwh battery. 5.2kwh of solar. I charge to 50% at night. My heating is electric and my system can run the house if there is a power outage. This week so far (Monday to Friday) I've paid £2 import and been paid £6.22 for export. And it's only been sunny for about 50% of the time. Also for the record the max from my panels coming in I have seen is 4kwh which impressed me a lot. My solar system has meant my energy bills are 25% of what they were. If you can get solar now. I really hope the price keeps going down so others can join in. 🤞

[@GaryDoesSolar]

Thanks for sharing this Richard - does my video persuade you to investigate fully charging your battery every night now?

[@lyndastokes2971]

I still can't work out if using Flux to charge my battery overnight is a good idea or not. I don't have an EV so it's either Flux with overnight charging or the normal variable input/fixed output tariffs. I just can't get my head around which is best

[@GaryDoesSolar]

Hi Lynda, if I had an EV, I'd be on one of the EV tariffs instead, as the overnight/early morning off-peak import rate beats every other tariff I've seen... But whilst I don't have an EV, I'm very happy with Intelligent Octopus Flux for the time-being. There's a lot of export going on (especially at peak times) so I'm expecting to see some decent revenue at the end of each month as we head towards the summer. And I honestly don't mind when Octopus charges my battery - I kinda just trust the system :-)

[@simoncove1]

I can’t get these tariffs as it’s a business address. We have 8.7kw solar and give energy 13kwh battery. We use about 8000 kWh and produce 5500kwh per year. Usage is Monday to Friday 8-5. I am actually thinking of agile octopus. But charging overnight and a second charge 2-4pm. I’m not sure if the extra cycles will harm the battery? The daytime charge is probably the most important ref the agile oct tariff as fees so high in the evening.if you have any thoughts that would be great and I’ll check out the software also 👍👍

[@GaryDoesSolar]

Thanks for your comment, Simon - so typically you should expect one half or one full cycle per day on Agile, which will still provide 17+ years of operation with a 6,000 cycle limit. Hope you like the software :-)

[@BlackBuck777]

Gary, thanks for another interesting video. I am currently in receipt of FIT payments which are based on a notional 50% export. Now I have a battery that's never going to happen 🤣 Do you think Octopus Go / Intelligent Go will support export payment if I am on the FIT scheme? Obviously that would be a nice additional benefit!

[@GaryDoesSolar]

Thanks for the great feedback. Now, I'm not an expert of FiT but worth joining this Facebook group and asking questions there as there are many people in that group who are on FiT: facebook.com/groups/2197329430289466/permalink/6080359505319753/

[@marktimmins3589]

Hello Gary, good job with the videos. I'm on my own experiment currently. I have PV, Powerwall and a ASHP. This week we have been self sufficient from solar with battery. No imports, but very little money making exports. Next week I'll set the TEG to maximise making money, ie, charge overnight and export everything with the Octopus Flux tariff. Hopefully it will force discharge between 4&7 (on top of exports in the day) with enough to get us through to the cheaper period. Luckily we have had decent sunshine this week.

[@GaryDoesSolar]

Thanks Mark - I'd love to hear how you get on with that... :-)

[@leehartshorn1479]

Even more to be gained if you force export the battery as well 😉

[@GaryDoesSolar]

Yes, I think so. Many people are suggesting dumping the battery shortly before midnight so that it’s ready for a full charge during the off-peak period…

[@fauxlobster]

Hi Gary. Do you find that changing the tariff mid year, so Flux during the summer and Go or IGo during the winter maximises the revenue from export?

[@GaryDoesSolar]

So, there are a lot of factors to consider, and if an EV tariff is involved, then the savings purely on the EV side might dictate the tariff choice. I made a series of videos here looking at strategies for tariffs that might interest you: kzbin.info/aero/PLJy1q7saPP7TaDCGrpg0yjFtHAN_UkCbz

[@MK_Maestro.1]

My panels will be on a southwest facing roof so will be maxing generation during the peak time of 4pm (to 7pm). So for a forced discharge to grid at peak time (4pm to 7pm) will the 6kW inverter be discharging the 13.5kWh battery at 6kW whilst allowing the 6kW panels to also discharge at the full 6kW?

[@GaryDoesSolar]

Unfortunately not. Your inverter limit will dictate the maximum export (ie 6kW) and solar power will get priority over battery discharge. So if you’re generating say 4kW with solar, the battery will add another 2kW to make 6kW.

[@wilteduk007]

I live in N.Ireland and it's so far in the past with tariffs that I'll probably be dead before they've introduced a smart/intelligent tariff. All export is limited to G98.

[@GaryDoesSolar]

That's a pretty poor show there - hopefully Octopus can make a difference there at some point...

[@prometheus4130]

is your flux example accounting for inverter losses of 7-10% ? my calculations are in those specific case its better to let solar charge the battery when guaranteed

[@GaryDoesSolar]

Yes, the generation data comes from PVGIS which includes inverter losses 👍🏻

[@Mimbultonia]

I’m on a FiT tariff- which makes it much harder to know if switching to a measured export will save me money over charging the battery. At the moment I am set up to avoid export whenever possible - but the advent of export tariffs make this much harder to figure out. Any advice?

[@GaryDoesSolar]

Sorry, I'm no expert on FiT schemes. Worth joining this group that likely has the answers you're looking for: facebook.com/groups/2197329430289466/permalink/6080359505319753/

[@Adventureshunterpandy]

Hi Gary, how do you get export costs of a £300 per day? Surely based on a 10 kW battery calculation would be 10×0.25 if the export rate is 25p ? Great video by the way. Thanks for doing this

[@GaryDoesSolar]

Thanks for your kind words? Not sure I quoted £300 a day (that would of course be most welcome!) Can you tell me where in the video please?

[@bazcurtis178]

I have been doing this following one of your previous videos. This month I have imported £22 and exported £30. I am very happy with that considering it is April. I turn my battery off 12am to 7am. I am normally now exporting by around 8am on a good sunny start to the day. Last year I was on Agile Export which was a mistake. I am now on the 15p export rate and that has made a big difference.

[@GaryDoesSolar]

Great to hear your experience, Michael. And yeah, it's a shame Agile Outgoing is nowhere near as good as Fixed!

[@bazcurtis178]

@@GaryDoesSolar Imported 80p today, standing charge 42p. I’ve exported £1.58 today and maybe another decent hour of export. I have made a profit 11 out of the last 14 days. Today has covered yesterday’s cost. If Agile prices were low tonight, I would force discharge, but today, will just top up.

[@markthorpe5831]

does this take into account the cost of approximately 10p per kwh per cycle on the batteries?

[@GaryDoesSolar]

Good point - the utility is configurable to include these costs or not. It's only applicable though to those who are considering buying a battery and using it in this way. I've made a few videos on that topic in fact...

[@ArryBradbury]

Is there a reason you weren't starting at 0% charge and ending at 0% charge? Surely utilising the full SoC during a day is the way to maximise revenue generation and therefore payback period for the solar/battery? Obviously limited by inverter capacity and number of overnight hours at the cheap rate.

[@GaryDoesSolar]

Yes, see 4m13s into the video for an explanation of the SOC setting 👍🏻

[@iareid8255]

Gary, when you charge a battery overnight you are using gas generated electrcity. Wind and nuclear cannot increase output becaus ethey are alreday at maximum available output and the balancing generation (Gas) will provide the power.

[@GaryDoesSolar]

Well, it depends on the country but in the UK renewables just made another record, and that’s average numbers across the whole day. So if we isolate to overnight, I’d say the chance of the energy used for charging coming from gas is very low. The real trouble is that there’s too much generation overnight and so wind turbine owners are paid to turn them off. I’d suggest that charging your battery overnight (along with hundreds of thousands of EVs) helps minimise that.

[@iareid8255]

Gary, no that is wrong. In fact the output from wind is on average very low. Because wind is uncontrollable it requires gas to keep the load and supply balance equal. On the rare occasion that wind is curtailed (Usually that is from the North sea as the grid capacity from Scotland to England is too small), on the odd occassion wind is generating strongly. Winds average per annum for the last two yeras is about 7Gigawtts from acapacity of over 20 gigawatts, it's abysmal. Not only that but technically inferior.

[@GaryDoesSolar]

@@iareid8255 Thanks for this - I very stand corrected. I just checked recent demand data overnight here: electricinsights.co.uk/#/dashboard?period=7-days&start=2021-03-11&&_k=asjr5m ... and I was a bit shocked to see that even overnight, there is still an almost constant element of gas generation! I'll do some further research on this tomorrow, but it does raise an immediate question in my mind for tariffs like Octopus Flux, which is designed for (non EV) solar and battery owners. Why encourage overnight charging if it results in more gas being burned?

[@iareid8255]

Gary, thanks for the frank reply. Generation as far as grids go is much more complicated now with the amount of renewables we have connected. Intermittency is the major, and I believe unsurmountable problem, the required battery capacity is simply far too large. Batteries have a part to play but consider Britains biggest battery, Dinorwic pumped storage power station in North Wales at 2 gigawatt power rating and about (From memory?) 10 Gigawatt hours of capacity. Essenntially and counter intuitively we don't really need much more. Renewables lack essential technical requiremenst for a stable grid. They are uncontrollable feeding a system that has to be finely controlled on an instantaneous basis. They have no inertia for stability , no reactive power contribution needed for a stable system voltage and have no short circuit current capability necessary for thetimely and proportionate operation of grid protection systems. You may be familiar with domestic requirement for earth loop impedance to be within a certain figure, so as to ensure sufficient fault current to operate the circuit breakers in the consumer unit. The grid is exactly the same. While supperficially, electricity can be generated in many ways, it does not mean that these methods meet the criteria for an economic and stable grid. Renewables simply do not which is why unit costs are now so high as they need considerable and expensive support from conventional generators.

[@rickeaston8963]

Ummm, what about round-trip losses? Does your calculator take those into account for various types of inverter?

[@GaryDoesSolar]

Yes, the utility allows for a percentage round trip loss value to be entered.

[@ascot4000]

It's the first time you leave me scratching my head Gary, so I will have to check my own numbers again. Whilst I do add 5 kWh to my SE battery in the Flux Off-Peak period, I don't fill it to full - I leave some remaining 'space' to reduce import costs and to allow room for the solar to top-it-up in the morning (normal day), or in the afternoon (a seriously bad day). For me the maths does not work if I charge from grid to full in the off-peak. The small cost difference between normal hours export and off-peak import are not sufficient to overcome the AC->DC efficiency loss when charging the battery from pure grid power. Indeed, the efficiency lost when filling the last 10 to 20% to achieve a 100% SoC is particularly noticeable; so I only allow that to happen with direct solar DC power. On a sunny day I have more of an issue with what to do with the excess solar. My 8 kW inverter tops-out at 10 kW AC - the house takes around 600W, so the remaining 9.4 kWh is off to the grid. The battery is usually full by this point but in the rare occasion it isn't, I still get 9.4 kWh going off to the grid but now the battery can charge from the otherwise 'clipped' DC as it bypasses the inverter limits. Even in April I have seen 11.4 kWh split between battery charging, house and grid. Not bad for an '8 kWh' inverter! I also don't empty my battery during the peak export period. Indeed, just half an hour (2.5 kWh total) produces noticeable income whilst getting the battery to overnight charging period with circa 20% remaining. I have also added some 'padding' times to allow the battery SoC to settle and, of course, it only gets to 100% once per day. Other than the fixed 5 kWh import and 2.5 kWh export period I am either off-grid or exporting power for the other 22.5 hrs in a day - come rain or shine. I'm still learning though and beating the SolarEdge controls to do exactly what I want is quite an effort!

[@GaryDoesSolar]

I'm glad my video has got you thinking :-) Now, one thing I didn't cover in that video was panel oversizing, leading to the clipping that you describe. A few people commented that it is better for them not to fill the battery to 100% too early, so as to avoid clipping. One way this can be done is to dynamically limit the charge rate of the battery. It's something I would need to look into in a lot more detail before coming to any conclusions, I guess...!

[@ascot4000]

@@GaryDoesSolar Dynamic limiting of the battery would be ideal but I am stuck behind the wall of SolarEdge controls. The normal customer-facing controls on the SE battery are both new and pretty-much useless. I have installer permissions that can achieve much more but even then I have to use time to control import and export rather than kWh or a percentage. I would prefer to have a system where I could instruct it to charge or discharge to a given SoC, rather than estimate what it depletes to and then add a set charging time at 5kW/hr to achieve roughly what I want. The lack of fine controls on the SE battery is the only thing I have against it; otherwise it is safest, most efficient and reliable battery there is. Frustration-free it is not. Over-sizing panels with a DC-coupled battery is a no-brainer. As we move to VtH and VtG charging in the coming years I would say it is essential. I aimed at getting 33 x 430w panels for an 8 kW inverter but the challenge of installing 3 panels meant dropping them at the design stage due to cost. I then lost 2 panels at the installation stage due to difficult joist spacing, leaving me with 'just' 28 panels. (My roof is very complicated: dormer-style with 4 different rooflines, aspects and pitches with numerous Velux windows, chimneys, obstacles and tree-shading issues. It needed an exceptional installer!)

[@kadmow]

Financially just do a sum of the forfeited feed in tariff vs the time of use off-peak tariff ss experienced - IF you are on "octopus" or some other market exposure plan - just ensure never to export in negative pricing, nor to charge during peak surge prices... (Environmentally - head to the hills and live in a cave...) I have no time of use offpeak (nor an automatically load shedding battery setup), and can ensure some energy whilst charging during the day - even in heavy clouds, half of my daytime charging will still be subsidised by the sun... In my country (Australia) - when assessing real market exposure (Amber Electric), we are often getting negative FIT - real wholesale pricing - during the day and still hit with the grid access charges for offpeak demand - arbitrage does something bt it does need significant investment to make pennies regularly...

[@GaryDoesSolar]

Is this a reply to another comment somewhere?

[@arpadvarga3475]

Thank you Gary! Superb help! According to your data I should really get one more 3.3 KW battery to have 9.9kw total! Which reflects the truth as winter time on our high usage days we run out of juice and we use peak rate electricity.

[@GaryDoesSolar]

My pleasure, Arpad - glad the video was useful to your planning :-)

[@arpadvarga3475]

@@GaryDoesSolar I don't stop recommending your chanel!

[@GaryDoesSolar]

@@arpadvarga3475 Thank you! 😃

[@twelvebears1971]

This approach is surely going to have to change if we get to the point where energy companies won’t want export during the middle of the day.

[@GaryDoesSolar]

I'm making a video on that very topic now...

[@chrisharper2421]

Hi, a quick question, do you take into account power storage inefficiencies? I have seen that power loss when charging and discharging could be 16%.

[@GaryDoesSolar]

I usually work on the basis of a 10% round trip loss in both my utilities and day to day monitoring of my own system. What make is your battery?

[@GaryDoesSolar]

Haha - my iPhone decided to autocorrect “usually” to “sexually” for some reason! 🤣🤣 Maybe I’m in love with my home battery!

[@chrisharper2421]

lol, battery are 3x PylonTech US3000C 3.5kWh 95% D.O.D and 1x Pylontech US2000 2.6kWh 90%DOD giving a total of 13kWh with 5.12kW panels south facing in north east England

[@chrisharper2421]

Just to advise, I found out how to charge my batteries from the grid, was a little difficult to find out how but once found it is quite simple. Worked a treat. So moved to octopus go which looked to meet our needs best, used your code. Now live and I estimate savings up to £700/year. Many thanks, your video inspired me….,

[@GaryDoesSolar]

@@chrisharper2421 That's great to hear! And thank you so much for using my referral code - very much appreciated! All the best with your solar journey and all those savings! ♥😃

[@robcole5805]

Hi Gary, thanks for the videos, always engaging. I've thought about this question a lot. I'm on Flux but tend not to charge overnight in the summer months. In fact I stopped this about 3 weeks ago. I just can't see the benefit of charging in the summer, as you say it depends on the individual set up, but for me I can't get away from the feeling I'm replacing 0% carbon electricity from my roof with emission creating electricity from the grid. As such, the economics may are the same but overnight charging results in a less optimal environmental outcome. Be interested to know if others disagree? Cheers for all the great work, Rob

[@peterjones6322]

I also have decided to charge every night and export the maximum amount. Octopus state that they only sell green electricity so you are in fact helping the grid more. Your daytime export lowers the use of gas generated daytime electricity and shifts your own consumption to the low usage period when there is very little need for gas generation, and is helping to balance the grid

[@GaryDoesSolar]

Great point, Rob! From what I understand from others, the grid is mainly renewables throughout the night (if you count biomass as renewables!) so perhaps not oo much of a worry. The benefit is really all about grid management, I guess - a flatter demand curve across 24-hours has to be a good thing...?

[@robcole5805]

@@GaryDoesSolar thanks Gary and Peter, certainly food for thought. I totally accept the grid balance argument, I guess I just like the idea of using the grid as little as possible. Cheers Rob

[@michael-nantwich4877]

Does your app factor in losses? I.e. My Powerwall losses 10% of the power charging and discharging, I buy 1kw at 9p but it cost 11p by the time I use it.

[@GaryDoesSolar]

Hi Michael, yes it does - configurable in the settings 👍🏻

[@antrog1895]

Hi Gary iv commented before re: batteries we were offered a 2nd battery for £1500 when we bought our system but we were already at £12k and basically thought how far do you go? Was disappointed when we saw a buy one get one free a few months later, rang up to see the price now’2k plus vat’ Just had an email offering an additional battery 1- 1485 - pretty much same now VAT been taken off 2-2550 3-3500 they’re only 3.2kw I know it’s more money but I really do like the buy it in the night sell at teatime 😁 what are your thoughts would we get our money back quickly? Once again ‘how far do you go?’ We’re on Octopus flux.

[@GaryDoesSolar]

My recommendation to everyone is always the same: research, research, then more research. Not just my videos, but online forums as well - any deals that look good, but aren't in reality tend to be quickly found out and reported on in social media forums like this one in the UK: facebook.com/groups/2197329430289466 In terms of achieving payback with a smaller battery, I'd recommend you watch this video I made: kzbin.info/www/bejne/q5LPqaeCgaaqmcUsi=2NH_Ng33eD6gkjtr

[@antrog1895]

@@GaryDoesSolar thanks ever so much

[@postiemania]

Great video Gary. I have solar and 48v FLA battery power.

[@GaryDoesSolar]

Thanks for the kind words!

[@mrmidland_traveller936]

Thanks Gary. Certainly confirms that what I've been doing is correct although there are some nuances that haven't been mentioned that can improve one's export gain. It's worth draining the battery in the evening once the sun has set as a forced discharge. Also, I prioritise sending excess PV generation to the grid rather than to battery storage. This also increases panel efficiency/yield as the panels generate max wattage for longer.

[@GaryDoesSolar]

That’s great insight - thanks! I think I’ll experiment with some of those ideas myself 👍🏻

[@deansh8506]

I've been doing this since SEG increased to 15p/KWh. Charge up my home battery overnight to 100% at 7.5p/kWh. No brainer really...

[@J555K]

Hi, How do you do this? I thought Octopus doesn't let you to have one tariff for import and one for export. If you have Octopus go with 7.5p/KW overnight, then your export tariff would be the "light" version so 8p/kw for export.

[@GaryDoesSolar]

Brilliant!

[@GaryDoesSolar]

I think Dean is talking about Intelligent Octopus Go...

[@deansh8506]

Yes Octopus Go Intelligent. I did try flux last year and force discharged my battery at the peak 4-7pm period. But to be honest it was too much faff and checking the weather, checking my battery SOC constantly. Also my overnight usage of electricity has increased as I on average recharge my EV 30kWh on a nightly basis. So my current setup suits me fine 👍

[@J555K]

Hi Dean, So you no longer able to export at a price of 15p/kW, right?

[@fabriziooddo9245]

Thank you Gary, another fantastic video. I am on Octo Intelligent and charge every night simply because you can't really predict PV generation and my ASHP eill kick in anyway early morning to heat the house before we wake up. Do you think it's worth exporting to the grid any remaining energy before the 23.30 off peak starts? Does it shorten the battery life if done every day?

[@GaryDoesSolar]

Hi Fabrizio - thanks for your great feedback! :-) Now, a couple of people have suggested the same - it does increase the daily overall income but it's at the expense of greater battery cycling (one full cycle instead of half or maybe 3/4). But you know with a 6,000 cycle limit, I don't think that's an issue. It's still 16+ years!

[@fabriziooddo9245]

@@GaryDoesSolar I think Givenergy (the battery storage that I have) gives 12y unlimited cycles warranty. They must know that tech is up to the game. Not the same thing but my first EV battery charged/discharged fully 100 to 0 every day (it was one of the first small EV with low range) resulted in a 3% battery degradation after 50K miles and 4 years of daily cycles.

[@stevepurcer4204]

Great information and analysis, Gary. I live in BC, Canada - can your solar and modelling utility be configured for CND and BC Hydro rates, etc.? We have time of use rates becoming active, and many of us with solar and batteries are very interested in using a tool like yours. Many thanks!

[@GaryDoesSolar]

Hi Steve, you're most welcome. Thanks for taking the time to watch. Yes, the utility is very configurable for all sort of tariffs. See what you think...

[@kpec01]

Hi, good application. could you add the ability to import the current agile rates?

[@GaryDoesSolar]

Thanks - and I'm working on that, yes... :-)

[@alanwood9804]

Makes sense even with Eco7, as Outgoing Octopus fixed export rate is currently 15p/KWh & E7 night rate is 13.31p/KWh inc. vat.

[@GaryDoesSolar]

Thanks Alan - I forgot to cover that tariff!

[@MichaelWakefield-mx6hg]

G'day Gary, great video as usual. I really like your channel, it's tech enough for geeks but straightforward enough for the less tech oriented. My comment is more of a request... I've been reading a bit about Nickel Hydrogen batteries, specifically as a home storage system. You may be familiar with this tech, but in case you're not, here's a short description: * developed by NASA and used in the Mars rover, the international space station, and the Hubble space telescope, along with many other satellites. * good for 30,000 cycles, or 30 years, at a 3 cycle per day rate * large charge and discharge rate. Not sure of % discharge available, but they talk of between 2 and 12 hour discharge available. * not subject to thermal runaway and will not explode or ignite * to date not used in terrestrial applications due to the high cost of platinum cathode, but a few years ago a scientist from Stanford university developed a low cost alternative to platinum. They claim production costs of $100 to $150 per KWh!! That's comparable to Li-Ion batteries * They're being commercialised by EverVenue in the US, and they're about to open a gigafactory in Kentucky. They are focussing on grid scale and commercial applications till now, but their residential products are under development. I would love to see your take on this very promising energy storage alternative to Lithium based batteries. Especially their longevity! Imagine solar panels, micro-invertors and a 30 year battery! You'd be set for life! Cheers, Michael Brisbane, Australia

[@GaryDoesSolar]

Michael, thanks very much for your very kind words about the video! :-) I'll do a bit of digging on Nickel Hydrogen batteries...

[@iansinclair7581]

Hi Gary, I managed to get a good deal on an EV. I called Octopus to see if it is worthwhile to change to intelligent Go. The lady I was speaking with reckoned I would be better staying off staying with Intelligent Flux as there is a cheap period between 2am and 5am. I have no idea what the tariff for this period is. Is it the same as ordinary Flux? I have not seen any info on charges during this period. Does anyone out there know?

[@GaryDoesSolar]

Hi Ian, I’ll be making a video on Intelligent Octopus Go soon… But I’d say if you can get on that tariff, and have a good sized-battery, it beats all other tariffs currently 👍🏻

[@GaryDoesSolar]

Great to hear about the deal on the EV btw! 😀

[@ChrisBrown-xf2ce]

Driving the weakest cell in your battery stack to the BMS charge cut-off point daily ain't doing it's SoH any good. Not much to be gained from going above 3.4 volts. But yes, what you suggest here is what a lot of people have been doing for a while now. I wonder why you didn't show an Agile example ;-)

[@GaryDoesSolar]

Home batteries are designed to be charged and discharged at least one cycle a day, so I don’t see any issues. I didn’t show Agile because my utility does support that tariff yet, but the results would have been even better, I reckon.

[@ChrisBrown-xf2ce]

@@GaryDoesSolar Battery cycles are marketing blurb. Energy throughput is what your battery warranty T&Cs is based upon (a few exceptions such as Tesla). I don't think Agile can beat IOG, but you can get close with Agile without spending thousands on battery storage to cover the whole on-peak period. Good luck with your Excel spreadsheet sales, you've put in a lot of effort with those.

[@GaryDoesSolar]

Yeah, fair comment on IOG - that’s a pretty difficult tariff to beat! 😀

[@stefanhorn6780]

I'm on agile and don't have an EV, but do have fixed price export of 15p , so as long as i can charge my batteries overnight for less than 15p, which is pretty much always.. i charge to 100%// also price tends to drop between 1200-1600 before spike, so i make sure i charge then as well.. working well

[@GaryDoesSolar]

That’s brilliant, Stefan 😀👍🏻

[@Wiljuchi]

Anyone got Octopus Go and not got an EV?

[@GaryDoesSolar]

Actually quite a few people are in that situation. The T+Cs allow Octopus Energy to claim back monies though, should they find out.