How Much Solar Do I Need For An RV or Off Grid Project: How To Get Accurate Calculations

Tom shares how he calculates solar needs for an off-grid or RV solar project to make the most of the solar system without overbuilding. Follow along in the detailed article on our website here - www.mortonsonthemove.com/how-...
Also, try our calculator and get access to our free email course - www.mortonsonthemove.com/rv-s...
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We are Tom & Caitlin Morton and we are the Mortons on the Move. We are co-hosts of 'The RVers' TV Show on the Discovery Channel, PBS, and Fun Roads TV. We are the Creators of the 'Go North' series available on Amazon Prime and KZbin. We've lived full-time in an RV since 2015.
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[@MortonsontheMove]

If your thinking about solar be sure to give our RV solar calculator a go for a basic recommended option and free course all about it! www.mortonsonthemove.com/rv-solar-calculator/

[@neitzp]

This is so good, so, so good. This information is exactly what I was hunting for and was not finding it, until now. Thank you!

[@g.r.2985]

It should also be mentioned that overweighting the rig will usually void your insurance in the event of an accident, but thanks for all the useful information!!

[@henrivanbemmel]

Perhaps, but I will bet my grandfather's shaving mug that half the RV's on the road are overloaded. Just like car filled to the roof going on vacation. Not sure how much this is enforced.

[@henrivanbemmel]

I had a discussion with a guy on weight limits for truck campers and he told me that these were all BS and that the vehicles can carry plenty more. I said why have the standards. He told me it was political. Dunno.

[@SuperSushidog]

How does that work. Insurance is supposed to cover you if you're at fault in an accident. This means that if I'm speeding, while drunk, run a red light and have an accident, making me clearly at fault, my insurance will pay. Yet if I'm overloaded making me at fault, my insurance won't pay? To be clear, I don't recommend anyone overloading their RV or any other vehicle. I recently added about 800 lbs to my motorhome with a huge solar battery system, (about the same as traveling with a full tank of water) but I removed about 400 lbs to allow me to do so safely. However, my tag axle motorhome has more carrying capacity than most TTs and fivers, to support the added weight. However, if one were to make a mistake and get in an accident when a couple hundred lbs. overweight by the manufacturer's suggested weight limit, I think the insurance would be forced to pay the claim anyway. Now if you happened to exceed the DOT legal axles weight limit (an entirely different and much higher standard of 20,000 pounds on a single axle, and 34,000 pounds on a tandem axle group) and you are involved in an accident, you will probably receive a citation for breaking this DOT law, nevertheless your insurance should still be on the hook to pay - just like if you ran a traffic light, breaking that law.

[@Kayyoumali]

Thank you for this plethora of useful information..

[@ro-cl2do]

Thanks Tom. I follow Mortons on Move and have not only learned a lot but also enjoyed the articles. I'm getting ready to add a couple of solar panels to help charge my 412 AH's of Lithium batteries so this video will help me. I do use the Watchdog and plan to estimate my usage with that. I will give your solar calculator a try. Thanks again.

[@brentjohnson6654]

Thanks for another great video. Very well organized as usual.

[@ManWander]

wow! a whole lot of useful info in this video! i hope to replace my agm with lithium some day but the thing about not charging below freezing is at this time preventing me

[@Bobs-bd3yo]

I live in Montana but spend most of time in the south in the winter. If you purchase lithium batteries with a built in BMS it shouldnt be a concern. In the 4 years that i have had battle born batteries i have not had a problem with cold temperatures shuting down below 32 farenheit and have been in 10 degree weather. Also most lithium batteries will alow you to continue to use the batteries to 0 farenheit they just wont charge below freezing and this is the battery temp. With this all said i am very happy with 400 amps and a 3000k victron inverter and have only used my generator a few times and even then I pulled trigger when i really didnt have to. My 1300 watts of solar keep everything up to a 100% by the end of the day even in the winter.. My wife uses the hair dryer,microwave, instant pot and convection oven. Its all doable and rarely hit 50% of the batteries draw.

[@rnordquest]

Note that using your battery will keep it warm. So if you use your furnace fan when it’s cold it’s unlikely the battery temp will get too cold to charge.

[@henrivanbemmel]

Yes, but I guess you need to consider when you go camping. Renogy now sells a 100Ah LFE batteries that has built in heaters, so you would be fine anyway. In my case we don't camp in the winter, so I swap out my 4 LFE batteries and bring them into the house for the winter and put the two LA batteries that came with the RV just to allow the DC circuits to run. I was fussing about trying to heat my batteries (I bought mine before the heated versions came out and they would not trade them) and realized that I would almost never use them in 20F weather so I stopped worrying. @RwHenri

[@adventureswithgnomie6553]

Great information!

[@mhspear]

we have a huge roof as we have no ac up there..we have 2200w solar and 860ah @24 lithium...and a hardwire watchdog..we are very thankful to people like you who put out these marvelous videos...we are power hogs+...just FYI...thank you

[@johnnylightning1491]

Thanks Tom. The critical factor for me is trying to convince the wife that we need solar, but that's probably a topic for a different video. Thanks for all of the good information, I think I'll have to watch this with the article and notepad to get the most out of it. Keep the good stuff coming and say hey to your wife.

[@henrivanbemmel]

It depends on how you camp. If you go to powered sites then forget it. If you are going to the boondocks with a generator, I assure you that the first trip you can do it without the noise she will be sold. All hobbies cost money. People blow $1000 on golf in a month. Starting with $2500 for two LFE batteries and 800W of solar will get you going if again your camping is unpowered. You only live once.

[@DennisWintjes2]

Thanks Tom! Like 342 The last part was not clear, or stated very quickly. To be clear, I heard that daily solar Kwh = battery Kwh. Is this correct? Ie. 1300Wh/day of solar=1300Wh battery (or one 13v 100A LiFePo battery).

[@travisn2it]

Where's the discount link for the power monitor?

[@annesaunders1157]

I have a Battleborn 100-amp hour battery and a Victron battery monitor. Where I am confused is how the amp hours drop even when I have solar energy incoming ( two 220-watt panels). My battery stops accepting a charge at a certain point so the amp hours will drop as much as 10-20 percent per day regardless. I have the charge controller set at the specs recommended by Battleborn. Is it odd that I can't get the battery to fully recharge amps when I otherwise have adequate solar to restore to full voltage?

[@henrivanbemmel]

Hello there. Thank you for your video. I have great respect for the work you have done to support RVing. We have a 35 foot gas class A RV and we camp about 1 month or so a year. We like to camp where there are no hookups, but that is less common in eastern North America. However, in the non-powered parts of campgrounds in provincial parks, they are often, more private, less busy and quieter than the powered sites. I feel that your computations are too close to the line for the practical reality of campsites and weather. I have 800W on the roof (4 pairs of two panels) leading down to a single solar charge controller to a bank of 4 x 100Ah LFE batteries. I have done the computations that you suggest in exquisite detail including modelling the solar angle and the expected power production not only by season, but during the day as well. My record is 263 Ah = 3.15 kWh in a day. I understand that you use Wh and you are correct it is a measure of energy. However, the metering that I have indicates Ah on the batteries and since my only voltage is 12V counting things in Ah is just easier as that is the unit of quasi-energy storage given on the battery meter. Whatever. Most campgrounds have trees and this can limit your solar gains in the AM or PM or for the day. So, for week long camping I came up with the following logic. The battery bank should enough to go for 3 full days without any charging if you are being careful. So in my case with around 100-120 Ah per day => 360 Ah =>? 400 Ah of battery capability. Given the parasitic loads that most RV's have and you are going to burn 40Ah (500Wh) a day doing nothing. So it is pretty hard if you are cooking or watching TV or charging computers to stay under 1200-1500 Wh/day and it can get out of control real fast on a rainy day. I felt that by using 400Ah of battery I could do a 4-day 3-night trip and not worry too much about power. I would come in fully charged and leave in the middle of the last day. So although we say it is a 4-day trip the burden on the electrical is really one day less. At the same time, even with shade and/or cloud I can usually get 30-50 Ah each day from the solar on the roof. Over a 3-day trip that is roughly the power needed for another day. So, with my set up the worst (almost) case would be 5 days and 4 nights before I need some help. We are usually not permitted to run generators in our parks (Ontario) so if I'm really flat I may have to leave and drive a bit and then come back in a few hours. So, for the solar, I recognize that each day is not going to be a 'blue sky' day, so I want to have enough solar to catch up at least two days of average use. My best peak power has been something like 680 W in July for an 800W panel. I found on my previous RV with only 400W you needed ideal conditions to be able to keep going. Having 800W really helps. So, If under reasonable sun angles, the panels will give me 200+Ah, that is roughly two days of use. The morning of day 2, you will have lost most of a day's use as there would have been evening cooking, TV/computer and fan use plus breakfast. So, starting on the morning of day 2 you will already be nearly 1 day of energy down. If the weather is inclement or even heavy cloud you might spend more time inside and use more power and then another night cycle. Now, you are down 250Ah on the morning of day 3 and you have had only 1 charge day that due to the cloud will be poor perhaps 50 Ah or less. Anyhow, the point is that the batteries get run down quickly and the recharge is iffy. So, if you are going to invest in solar to allow camping at more remote sites, you want to have the batteries for sure and then enough solar to bring them back in a reasonable time. In the battery charge game you are always in debt, trying to pay off yesterdays debts! If money is tight for this, remember that the batteries are the expensive part. So, design the system first and install all the solar panels you are going to need going forward. Make sure that your charge controller is the right size for the array you put in. I suggest that you get at least two LFE batteries as a start and then you can add them when they go on sale or perhaps Santa will buy you one. Money arguments do not change the laws of physics. You are going to use MORE power than you think especially if you have family and kids. Having lots of panels to almost for sure charge your two batteries every day will give you the fun of this while you are building the system. Having more batteries allows me to camp where there is some shade and be able to make it. Finally, the figure of 350 Wh per day is an IDEAL one and this will only occur in bright sun with no cloud or shade. Now, that may be the reality of where you camp, but for most of us it is hugely optimistic. I would cut that number in half at least given shade, panel debris accumulation while camping (ie leaves), clouds and so forth. I would rather tell folks the unvarnished truth rather than get them started and find out that nope, you really can't do this for much less than 2 LFE batteries and 800W. In Canada, I would pay 1700+900+350+150 = $3100 CAD =~$2400 USD. Also,. as I did not want to run wires for a fixed meter in this RV, I bought Victron's 'Smart Shunt' which sends a Bluetooth signal to my phone and I can read my battery info the Renogy controller also has a BT accessory that does the same. It is nice because I can check it on my phone anytime I'm near buy and not have to go to a meter. These apps also have history on them as well and are free. Thanks for your work. You are amazing. BTW we bought a Chevy Volt 2017 based on your video describing the car. We live in Ontario 300 km north of Toronto and there are hardly any charging stations. The car works well for local trips and then the gas cuts in for longer and still gives a good rate. We drove 4000 km last summer for about $400 CAD = ~$300 USD not bad. I had a hotel room cost me more for just one night. So far ... the car has been great! Henri (RVing with Henri @RwHenri)

[@thefinalboss2403]

Another tip is to never buy an rv as they are all overpriced junk. Build your own. I work on all sorts of RVs and i have never seen such cheap build quality. If you wanna spend a quarter million on a rig made out of popsicle sticks and staples go for it. Ill be laughing as you drive by.