Why consider a true sine wave inverter for your off grid power project? There are several reasons to consider. First are the advantages they provide in running any appliance with electric motors. Second, are the advantages for your home electronics and stereo. The third reason to consider them is the fact that many manufacturers are producing these inverters at a lower cost so the price difference between true sine wave and modified sine wave inverters is dropping steadily.
Thanks to contributions from readers, we have some qualified information that spells out just how much better motor appliances run with (True Sine Wave)TSW. When you run a refrigerator with a modified sine wave, there are side effects related to harmonics and the power factor. The power factor simply means the voltage and current are not synchronized. A true sine wave inverter can run a larger motor than a (Modified Sine Wave)MSW unit of the same rating. Here is what one reader found for an unusual inverter load – an air conditioner. Not the best thing to run with an inverter and batteries, but a large electrical motor load.
“… Turns out they had only tested our MSW Prowatt 1800 model so I gave them the Pure sine inverter from our booth and asked for a lab test report. To everyone’s amazement they realized a 20% improvements in run time on a full charge of the same battery. “
The reason that TSW inverters are more efficient is that they don’t generate the harmonic or extra frequencies beyond the 60 Hertz for the AC power. Those harmonics created by the MSW tend to create extra heat in the windings of electric motors. Extra heat means wasted power, and a shorter service life, especially in warm environments.
Note: [Running all our stuff on MSW for the last 11 years, its hard to say exactly how much shorter the refrigerators have lasted and why. Our Magic chef 10 cu foot unit only lasted 5 or 6 years. How much was due to equipment quality, and how much was due to heat from MSW is unclear.]
Clearly, there are advantages running things like an off grid dishwasher or running a well pump on TSW power. These gains can shrink your power system, or better yet, have extra power for other applications!
Will my home electronics benefit? Yes, especially if you are a fan of high fidelity stereo music, or listen to AM or shortwave radio. The extra frequencies beyond 60 Hertz created by MSW inverters quietly crawls through the wiring and makes it into your audio equipment. The degree this happens varies depending on the type and model of equipment.
For example, on our stereo it tends to be very mild. But if you listen to no music you’ll hear that 60Hz hum. On the other extreme, I have some amplified PC speakers that I threw away, and were recycled for use on my son’s computer. The no input hum is so loud, I keep threatening to toss them if he doesn’t keep them unplugged when not in use!
The MSW harmonics also tends to use the house wiring as a radio noise antenna for low frequency AM broadcasts or short wave reception. When I tried to do some amateur radio work on 20 meters, I had to turn off the house power to pull in any stations over the noise.
So is a true sine wave inverter more expensive than than the modified sine wave inverters? Unfortunately, yes. However, that price difference is steadily dropping as demand increases for TSW. 5-10 years ago, there were only large TSW inverters available, but now even Xantrex offers a smaller 600W unit to meet the need to run home electronics on clean power!
If I could wave a magic wand and re-design my off grid power system, I’d certainly go with the higher cost true sine wave inverter as it would save power and annoyances for years to come.
Would you pay more for the advantages outlined here? Why not get one of these 600 W units for your SEGS(Small Emergency Genverter System)? How are your power system plans going? What questions do you have? Tell us below in the comments!