Inverter basics and choosing the right model

How to choose an inverter for a solar system.

Covers sine waves, modified sine waves, grid connection and backup power.

We offer many types, sizes and models of power inverters. Choosing which one is the best from such a long list can be a chore. There is no "best" inverter for all purposes - an inverter that might be great for an ambulance is not for an RV. Power output is usually the main factor, but there are many others.

There are many factors that go into choosing the best inverter (and options) for your application, especially as you move into the higher power range (800 watts or more). This page should give you the information you need to choose the option that is best for you.

We offer standard residential and light commercial inverters, as well as mobile/RV/marine inverters.

different types of inverters

Pure Sine wave, Modified sine wave

Pure sine wave

Modified sine wave

Pure sine wave, Modified sine wave.

There are 2 main types of inverters - sine wave (sometimes called "true" or "pure" sine wave), modified sine wave (actually modified square wave)

Pure sine wave

The sine wave is what you get from your local utility company and (usually) from a generator. This is because it is produced by rotating AC machinery, and a sine wave is a natural product of rotating AC machinery. The main advantage of a sine wave inverter is that all devices on the market are designed for sine waves. This guarantees that the device will work to its full specification. Some appliances, such as motors and microwave ovens, can only produce full output with sine wave power. Some appliances, such as toasters, dimmers, and some battery chargers, require a sine wave to work. Sine wave inverters are always more expensive - from 2 to 3 times.

But the sine waves they produce are closer to the AC power provided by the electrical outlet in your home. Some devices, such as uninterruptible power supplies, may not function properly without a stable pure sine wave.

Modified sine wave

These inverters are the more affordable of the two. The "modified sine waves" they produce are perfect for most consumer electronics, so they work well in many different applications.

The modified sine wave inverter actually has a more square wave waveform, but with an extra step size or so. A modified sine wave inverter will work fine on most devices, albeit with some reduction in efficiency or power. Motors like refrigerator motors, pumps, fans, etc. will use more power from the inverter due to lower efficiency. Most motors will use about 20% of the power. This is because a considerable proportion of the modified sine wave is a higher frequency - that is, not 60 Hz - so the motor cannot use it. Some fluorescent lights won't be as bright, and some may hum or make an annoying hum. Devices with electronic timers and/or digital clocks often do not function properly. Many appliances get their time from line power - basically, they take 60 Hz (cycles per second) and divide it into 1 time per second or whatever frequency is needed. Because modified sine waves are noisier and rougher than pure sine waves, clocks and timers may run faster or not work at all. They also have some wave parts that are not 60 Hz, which can make the clock run fast. Items such as toasters and dimmers may not work at all—in many cases, appliances that use electronic temperature control cannot be controlled. Most commonly, variable speed drills have only two speeds - on and off. Items such as toasters and dimmers may not work at all—in many cases, appliances that use electronic temperature control cannot be controlled. Most commonly, variable speed drills have only two speeds - on and off. Items such as toasters and dimmers may not work at all—in many cases, appliances that use electronic temperature control cannot be controlled. Most commonly, variable speed drills have only two speeds - on and off.

Other notes:

Since most cars and trucks are not really designed with inverters in mind, it is important to avoid overloading the system. An important factor to consider is the capacity of the battery. If the inverter is used when the vehicle is not running, it will drain the battery quickly.

Some trucks have extra space under the hood for extra batteries, which helps reduce the impact of using the inverter when the vehicle is not running, but that's not always an option.

While using the inverter while the vehicle is running allows the alternator to keep the battery charged, it is also important to avoid excessive alternator usage. Since alternators are typically designed to provide enough power to run all the electronics in the vehicle and keep the battery charged, they may not have enough extra capacity to run a powerful inverter.

The best way to avoid this problem is to check the rated output of the alternator and then buy a suitable inverter. If that's not enough, you can replace the OEM option with a higher output alternator.