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There are two types of inverters, pure sine and modified sine wave. Pure sine wave inverters offer better performance but are more expensive, but can you run an air conditioner on modified sine wave? or do you really need pure sine wave?
Appliances such as air conditioners, refrigerators and microwaves will not work on a modified sine wave inverter because the current does not flow efficiently. Even if you can get an air conditioner to run, the compressor is going to overheat and get damaged.
How Do Inverters Work?
To understand why modified sine wave is not ideal for AC units, we need to look at how they work.
When you plug an appliance in an AC (alternating current) outlet, it runs on 110V or 120V. Batteries used with solar panels are 12V DC (direct current).
What a pure and modified sine wave inverter does is convert the 12V DC into AC, or at least something like it. When DC is turned into AC, the appliance can run from the battery.
The changes in AC power direction can be thought of as a sine wave. In a pure sine wave inverter, the polarity switches smoothly, with gentle curves. With a modified sine wave the polarity change is abrupt.
The more the polarity change resembles a real sine wave, the more it is capable of handling sensitive electronics. Modified sine wave inverters are easier to make and cost less. The drawback is some appliances and AC motors are sensitive to the sudden polarity shifts and prefer the gradual type.
The sudden shift can be jarring to AC motors and affect performance. The abrupt polarity switch affects the current that goes into the motor.
What Happens If You Run an AC on a Modified Sine Wave Inverter?
Pure and modified sine wave inverters do the same thing, convert DC to AC. The difference is the process as described above.
Appliances that use alternating current (AC) motors and compressors do not run well on modified sine wave inverters. Even if you are able to start up an AC unit, it will not function at full capacity.
Medical equipment are not designed to run on modified sine wave inverters either. If the appliance does not have a motor and not for medicine, it can run on modified sine wave.
If you have a large window or central AC, you will likely end up buying a pure sine wave inverter such as the GoWISE 2000. A typical window AC system needs a 2000W inverter minimum to run, and most of them are pure sine wave.
A portable air conditioner can run on a small inverter, but even then we recommend pure sine wave. It is less about the watts but more about the compressor.
Some will argue that it will take a long time for modified sine wave inverters to actually damage an AC. That could be true, but some AC units are more sensitive to current than others and may need pure sine wave.
It goes back again to whether you are willing to take a chance. While AC unit costs have dropped you still want to get the maximum production from it. And the way to do that is to use a pure sine wave inverter.
How Modified Sine Wave Inverters Can Damage an Air Conditioner
Air conditioner compressors, like those on a refrigerator, are sensitive pieces of equipment. They are designed to run on 110V or 120V, not on converted 12V DC power.
Are there cases where modified sine wave inverters run AC units? Yes, it is possible. But you risk damaging the AC compressor or shortening its lifespan.
At the very least the AC will not run at full capacity. You can set it to maximum power and it will not perform to its potential.
This forces the compressor to work harder to cool the area, stressing its components. During very hot days the motor can overheat and cause permanent damage.
You are probably wondering if this applies to central and window AC units only. Maybe a portable AC can get by with a modified sine wave inverter.
The answer is it might work. But we can say the same thing for a refrigerator, or any other appliance that uses an AC motor. It could work but is it worth taking the chance?
You can think of it as running power tools on an inverter. You can do it with a modified sine wave but the tool will not run at full power. The same applies to air conditioners.
Another issue that can arise is noise interference. Inverters usually produce a slight humming sound, but it gets drowned out in by ambient noise.
Air conditioners running on modified sine wave generate a lot of noise. This is more of a nuisance than anything else, but a loud air conditioner can get annoying real quickly.
What Appliances and Devices Run on Modified Sine Wave Inverters?
If the device or appliance does not have an AC motor and not used for medicine, you can run it on modified sine wave.
Most of the time you don’t have to worry about this. For TVs, laptops, lights and other appliances modified sine wave is fine. But here is the thing. If you are installing a solar array in your home, you will probably run most appliances on the inverter. And that includes the refrigerator, air conditioner and microwave.
Since those appliances need pure sine wave, it makes sense to just buy that inverter. There is no point in using pure sine wave for the AC and fridge and modified sine wave for the rest.
AC on Modified Sine Wave inverter Likely Scenarios
Suppose you have a window AC and connect it to a modified sine wave inverter. Any number of things can happen but the following are some of the most likely.
The AC will not even start. Compressors vary but highly sophisticated components need pure sine wave. The inverter will not be able to load the AC even if it has enough power.
If the AC does start, expect to hear loud noises. It can be a buzzing sound or just some loud noise coming from the unit.
There is nothing wrong with the AC or the inverter. The compressor just doesn’t want to run on modified sine wave. it can work, but the sudden shifts in polarity affect its performance.
But what happens if you just ignore the noise and keep the AC on? The AC might continue going if there is enough power in the inverter. But it will cause long term damage to the compressor.
By forcing an AC to run on a modified sine inverter, the compressor has to work harder. An overworked motor compressor is prone to overheating, and we know that is not good for air conditioning systems.
This scenario is for AC units but is also applicable for other appliances with alternating current motors. Running them on modified sine wave puts undue stress on the appliance and has a detrimental effect on performance.
Will this damage the inverter? Probably not, but there is the chance you could destroy both the appliance and the inverter. So for AC units, motor powered appliances and medical equipment, pure sine wave inverters are ideal.
Tips For Using Air Conditioners with Inverters
Make sure the inverter power source has enough power to run the fridge. If you are on the grid you can turn to electrical power if solar production is insufficient. If you are off the grid, the battery bank must be fully charged to run the load.
Even a pure sine wave inverter needs plenty of power to run an AC. Do not forget that air conditioners have startup power requirements which could be twice that of its running watts.
Modern air conditioners have no problems running on pure sine wave inverters. The only question is how much power will be used. Remember that the air conditioners- or any appliance – draws more amps from a battery than an AC power outlet.
There is a lot of debate on whether you should get a pure sine wave or just stick with modified sine wave inverter for air conditioners. While you might be able to run an AC on modified sine wave, why risk it? For peace of mind you should get a pure sine wave inverter.