Low Frequency Vs. High Frequency Inverters

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In this video, I'm going to show you the difference between low vs high frequency inverters, focusing on their efficiency and advantages. We'll dive into various criteria such as weight, applications, lifespan, and price to help you determine which type is best for your off-grid solar system needs.
First, we'll discuss low-frequency inverters (LF). These inverters are generally heavier because they use larger transformers. For example, a low-frequency 12V 1000W inverter can weigh around 35 lbs (16 kg). They typically have higher idle power consumption, though Victron is an exception with its efficient design. Low-frequency inverters are ideal for systems with inductive loads like air conditioning, electric motors, and compressors. They have a longer lifespan and handle surge power better, though they are usually more expensive due to the copper coils.
Next, we’ll look at high-frequency inverters (HF). These are lighter, using smaller transformers. A high-frequency 12V 1000W inverter weighs about 6 lbs (2.7 kg). They generally have lower standby idle consumption, making them more efficient for systems with resistive loads like lights or kettles. However, their lifespan is shorter due to the electronic components, mainly capacitors, and they are less capable of handling surges. High-frequency inverters are cheaper because they use less copper.
A high-frequency inverter uses MOSFETs for electronic switching, which require cooling via heatsinks. You can see these components in the picture.
When choosing between a low-frequency and high-frequency inverter, consider your specific needs. For example, Victron combines both technologies in their Hybrid or Combined High Frequency inverters, offering low idle power consumption. Aims uses low-frequency inverters, while most Growatt inverters are high-frequency, with some exceptions.
If you’re unsure whether an inverter is low or high frequency, check the weight. A 3kW high-frequency inverter weighs about 13 lbs (6 kg), while a 3kW low-frequency inverter weighs around 42 lbs (19 kg).
In conclusion, I recommend using a low-frequency inverter, preferably from Victron, due to their low idle power consumption and reliability.

[@curtchase3730]

One reason the low freq inverter is "better" for heavy inductive loads is that the big heavy power transformer, being a huge ball of wire, is nearly indestructible from a short overload. If the device trying to start ( ie: air conditioner, table saw, freezer, etc.) approaches the output limit of the inverter, a voltage sag will be the result and a trip condition may result. A hi freq inverter, when subjected to a similar load, will try it's hardest to fight off the surge and make the device happy while actually failing and blowing up all it's MOSFETS trying! No different than vacuum tube circuits VS transistor counter parts!

[@jimmurphy5355]

Yeah, but no. I have designed AC power conditioning and regulating products, and the transformer in "Low Frequency" inverters is NOT what gives them the ability to handle surges. In general, low frequency inverters do handle surges better, but the reason is because the number and ratings of the FETs driving the big transformer. I don't know WHY the designers of high frequency inverters skimp in that area, but if they didn't, it would be totally practical to make one that had just as much surge cpapacity as a low frequency inverter.

[@xtneuron]

Any high frequency inverter that self destruct when overloaded was poorly designed. A low frequency inverter will equally be damaged if the power switch rating is exceeded. Sturdier designs always have current limiting circuits.

[@curtchase3730]

@@xtneuron Thanks for the info! Yes, makes sense. I figured a low freq inverter would have fewer parts to fail, but I guess not. I agree that just about all budget Chinese hi freq inverters are designed to just barely hit specs but cheaply. They allow no room for any overloading. They also have piss poor isolation and RFI suppression. Some are so bad that even the neutral leg is floating and if it is bonded to ground...POOF!

[@jimmurphy5355]

"Pure sine wave" Low frequency inverters are now the most common type. Just like high frequency inverters, they use FETs to synthesize a sine wave by using pulse width modulation. They have exactly the same electronics complexity as a high frequency inverter. Both low and high frquency inverters switch their FETs at very high frequency, so the term "low frequency" can be a bit misleading. The real difference is that high frequency inverters use a DC-DC boost converter to create ~350 volts DC, and then use FETs to switch that high voltage on and off very rapidly to create the 120/240 VAC. Pure sine Low frequency inverters use high speed FET switches to rapidly turn the battery voltage on and off to create a low voltage 50/60 Hz sine wave. That low voltage sine wave is stepped up with the large, heavy low voltage 50/60 Hz transformer/

[@cleversolarpower]

Indeed, I didn't put this in the video because people would fall asleep 😀. The term "low frequency" in inverters can indeed be misleading. While low frequency inverters do use FETs that switch at high frequencies, the key difference lies in how they convert and manage power.

[@jimmurphy5355]

@@cleversolarpower Low frequency inverters also have another capability that most high frequency inverters lack: They can absorb AC power on the output side, and feed that power backwards through all the inverter circuits and charge the battery. This means that a low frequncy inverter can act like the grid. If you have an existing solar system that is grid connected, and is has only AC output, perhaps because it is built with microinverters under each panel, it will shut down when the grid fails. If you add a battery and a high frequency inverter to such a site, the solar panels are still useless. They can't charge your battery. But if you add a battery and low frequncy inverter, the AC power from your solar system can flow backwards through the inverter and charge your battery. For anyone who dove this deep into the comments - look up "AC coupled solar backup" for the details. For me, this feature of low frequency inverters was the key factor that made that type mandatory for my situation. I had a large grid-tied solar system at my house, and wanted to add a backup system that would enable that system to work even when the grid was down. So I added a 5 kW low frequency inverter, and it does exactly that. The solar system "sees" it as a grid, and fires back up, and pushes its output to the inverter, which accepts it, just like the real grid would.

[@AnonJohn143]

Informative and helpful. Thanks as always mate.

[@cleversolarpower]

My pleasure!

[@quickquote1568]

Excellent video on the difference between high and low frequency inverters. Low frequency make a much better choice for real world use.

[@lawrencedavidson6195]

Thanks for this useful information. Greetings from an amateur solar hobbyist in Jamaica.

[@cleversolarpower]

Thanks for watching!

[@chriserb2645]

Ty for the info!

[@adon8672]

Apart from Victron, which other company makes low (or hybrid low-high) frequency inverter with little idle power consumption?

[@E9_G]

Now that we have inverter washing machines, inverter pressing irons, inverter air-conditioners, inverter fridges and freezers, isn't the concern regarding surges becoming baseless by the day? All the aforementioned devices I own are all inverter devices so I am more inclined towards the cheaper High Frequency option. Is there not enough rational in my thinking?

[@Madsci-zy8wm]

No because the inverters in the devices that you mentioned are inductive loads.

[@E9_G]

​@@Madsci-zy8wmSo are you saying that it is inconsequential despite the fact these devices are of inverter type as opposed to the traditional type? Did you understand what I meant by inverter devices, which is clearly how they are branded by their manufacturers and quite rightly so?

[@ruslanwel]

you're right, also my power tools without inverter has soft start (but what about soft end :)), I think it also helps but...I choose low-frequency :)

[@danielking2944]

I have several of the Growatt 5K inverters and have to use transformers to form neutral for 120v loads. The transformer adds a bit of boost when starting inductive loads although that wasn’t the original purpose. I’m running two 18000BTU mini split heat pumps on one and am planning to add a third. Because of the inverter design of the heat pumps they don’t seem to have any start up surge. This particular inverter doesn’t need a transformer because the heat pumps are 240v.

[@cleversolarpower]

Good to know, thanks for sharing!

[@rilosvideos877]

One important question remains open: who are low and high-frequency combined, e.g. in Victron? How do they achieve low idle consumption beeing low-freq. inverters? They combine PWM with a low-freq. transformer in the end-stage. We need to understand how this works!

[@isettech]

Not mentioned is the harmonic content. Many of the new high frequency inverters are true sine wave output.

[@henkmeiring01]

Three years back i was sceptical about high freq inverters.That is why i bought four and two sets of lead acid batteries .Two inverters per battery pack .For breakdown reasons.So far no problems.A friend of mine have one that is in its sixth year.And its very cheap.Prices between 200 and 400 dollars each.Depending what type of built in charger it have.If i convert South African money to dollar. But both of us avoid microwaves,electric stoves,toasters.Cant utilize it anyway because of low battery capacity.And batteries extremely expensive.

[@cleversolarpower]

If your loads are low compared to the power rating of the inverter, then that will also extend the lifespan. Maybe thats happening in your case. They can last up to 10 years as well.

[@bentheguru4986]

The biggest restriction is the battery config you have, fine if you are on 12, 24 or 48V, screwed on anything else.

[@brushbum7508]

Good Morning ! Thank You. TAKE CARE..

[@MarkSpohr]

How does a high frequency inverter make 50 or 60 Hz AC ?

[@cleversolarpower]

The MOSFETs switch very fast to create a sine wave. That's why it's called high frequency. Imagine a modified sine wave with the visible steps in between. MOSFETs in a pure sine wave high frequency recreate a sine wave by switching very fast.

[@MarkSpohr]

@@cleversolarpower Thank you

[@stephenhickman9502]

If your inverter struggles to power a microwave oven, it's likely an HF inverter. 😆 like mine. My inverter will run my microwave, but it stumbles at first for a few seconds.

[@eugen-m]

Big like 😉❤

[@scoobyblu5815]

Are you working for victron?

[@cleversolarpower]

No, but I'm a fan of their equipment. High quality, many options, good customization,...

[@adon8672]

Why are the vast majority of inverters these days (including off-grid, Grid-tied, hybrid and even industrial inverters) of the high frequency type? Could it be that longevity isn't that big of an issue afterall?

[@NigelM18]

Longevity is never a priority for any electronic device made today. They want it to break so you have to buy another one.

[@cleversolarpower]

Grid tie is low frequency. They should last you about 10years. That's the standard warranty period in Belgium. The reason they last so long is that they don't have to supply surge power because the grid takes the surge demand. Off grid is less forgiving. Imagine you are on a boat and your inverter fails. Dependability becomes more of a factor then.

[@albertorodas6479]

For fish farming you need 365/24/7 availability air supply.

[@seymourpro6097]

Shipping weight rules! Shipping from China is always priced according to the weight of the container.

[@adon8672]

@@seymourpro6097 I beg to differ. In shipping, volume is more important of a greater concern than weight. Shipping weight also doesn't explain why even US based manufacturers like midnight solar are gravitating towards HF inverters.

[@Kosmonooit]

Victron all the way! Although not the cheapest but an excellent product

[@cleversolarpower]

Yeah, it's reliable.

[@john0270]

Other than my chicom inverter handles my microwave, space heater, coffee pot , vacuum cleaner, grinders, saws, fridge, freezer, window ac ect ect ect.... where as the double the price victron phoenix 1200....... not a chance. Charge controllers seem to be great though, super flexible/programmable.... have 6 of them 😂

[@adon8672]

Why do low frequency inverters always have relatively high idle power consumption?

[@curtchase3730]

Most likely, the big heavy power transformer has inherent loss compared to a hi freq unit.

[@jimmurphy5355]

The large, heavy 50/60 Hz transformer has an iron core. The direction of the magnetic field in the core has to alternate at the mains frequency. That alternation induces losses in the iron - think of it as being something like friction in the alternation if the magnetic domains in the iron. These losses are directly proportional to the amount of iron, and are typically 4 watts per pound of iron. Core loss is independent of the load on the inverter.

[@adon8672]

@@jimmurphy5355 thank you for the this response. Probably the best answer to this question so far. Forgive me for asking further questions out of this answer. How's is Victron managing to keep idle consumption low, even better than many low end HF inverters? Are they somehow reinjecting the (potentially) wasted power in the iron core back into the system. I apologise if these questions sound naive but I'm really curious.

[@jimmurphy5355]

@@adon8672 I honestly don't know. The core losses can't be recovered - they heat the core, and they are gone. My best guess - and it is just a guess - they don't power the low frequency unless the load is demanding power. Some "low frequency" inverters have a power save mode that does that. Or maybe they use (expensive) ultra low loss grade iron in the core, and/or run the core at relatively low flux levels (also expensive because then you need a bigger core.) The true but not very infomative answer: better engineering and better quality components.

[@adon8672]

@@jimmurphy5355 thank you for the prompt and wonderful response. There's a lot of sense in your guesses and they are good enough for a lay person like me.

[@michaelagbayani4961]

Low freq is better the idle is not that big a diff some HF has higher idle load vs low freq inverters

[@cleversolarpower]

Indeed, like i said in the video it depends on the manufacturer.

[@deadgamer9808]

In india high frequency inverters are much more expensive approximately twice as expensive

[@cleversolarpower]

Maybe there is a high import tariff going on?

[@deadgamer9808]

@@cleversolarpower yes but i think its also due to lots of indian companies manufacture low frequency inverters and they are not importing it nor they are making them ( maybe because they have to set up new plant for it also they have to discontinue their existing plants which will be not be good for business) and the one who are importing them are charging premium

[@yannickbouhier9951]

my growatt invrerter die after 3 month ; it cannot support the 35 degree of philippines !!!!!

[@cleversolarpower]

It could also be that it ran inductive loads which puts stress on the MOSFETs. 35 degrees Celcius is not that high for electronics when it's well ventilated.

[@henkmeiring01]

​@@cleversolarpowerYou are right.In summer we regularly hit 45 degrees.And my 3kw /24v inverter keeps running.With hosehold items like fans,fridge,freezer,tv.And 600w water pump.Reaching 1000w all together.Most likely problem for breakdown is when you utilize over 2kw all the time.

[@TechnoEveryday]

❤🎉❤🎉❤🎉❤

[@scoobyblu5815]

For two years non-stop my high frequency 5000 watt inverter powers my whole house and makes my hot water and it was cheap as f...I You need to redo the video 🤔

[@cleversolarpower]

2 years is nothing though. Heating water is a resistive load, so no surge power is required.