Low Frequency Vs. High Frequency Inverters

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.

[curtchase]

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!

[E_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?

[quickquote]

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

[rilosvideos]

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!

[lawrencedavidson]

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

[danielking]

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.

[adon]

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

[AnonJohn]

Informative and helpful. Thanks as always mate.

[jimmurphy]

"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/

[Hikebike]

Thanks for this. I'm setting up a solar emergency system for prolonged outages but not regular use. I have a have h freq giandel 600w that I bought 2 years ago and tried on our basement tv. It's an old plasma. The wattage goes from 150 to 300 depending o on screen brightness. For some unexplained reason the inverters fan will not come on. So I bought a Victron 500w thinking it'll be

It won't power the TV. Relays in both the TV and the inverter click on and off but it will not power the TV. Very confusing and not sure what to do. I think it's because it's a non linear load? I kinda understand the concept. What's a good hi freq inverter brand?

[isettech]

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

[johnx]

High frequency inverters have problems with inductive loads and load balancing. So if you have more loads on one 120v leg or you run a power saw, these inverters can shut down on you. So you end up having to over-size your system to compensate and end up paying 10x as much, as compared to a low frequency inverter.

It’s annoying that we don’t see any all-in-one outdoor rated low frequency inverters on the market, and it seems when manufacturers address that, they move to high frequency models, which will have the same issue with load balancing and induction.

[Kosmonooit]

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

[bentheguru]

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

[henkmeiring]

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.

[samueladitya]

will High Frequency hybrid inverter last if the load is light inductive loads, like 0.5 hp water pump or 1hp Air conditioner using a 5kw rated hybrid inverter, If the surge load is assumed 5 times the rated load that will be 3.7kw at most, and that is still smaller than the power rating of the inverter it will last right?

[majharulislam]

Low frequency Inverters at no load may have mechanism to isolate the Iron core transformer to minimize the core loss. But in run time it will be in line and this core loss will be significant compared to high frequency Inverters.

On the otherhand, as Iron core have large voltage regulation at over load condition during surge power, hence limiting primary side current of iron core transformer through FETs. Ultimately, can take care of any high torque inductive load in the starting time without damaging inverter ckts.

[MarkSpohr]

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

[brushbum]

Good Morning ! Thank You. TAKE CARE..

[adon]

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?