Off Grid Home Forums Technical Discussion Inverters for Computers Reply To: Inverters for Computers


I design and build modified and pure Sine wave inverters. In 8 years I have blown two DVD players, two desktop computer power supplies, and one directv DVR box using a Samlex inverter. When I ran tests on this unit I found the appliances running from it were using 10 percent more energy then they did on the pure sine wave unit. We run our main house on a Xantrex 4024 pure sine wave unit now.

Power supply capacitors have a hard time with modified sine wave, but let me clarify. Some modified sine wave inverters use a softer waveform. They try and taper down the hard square waves into a more reasonable stepped pattern to make it easier on appliances to handle. Square wave forms that simply alternate between positive and negative are very hard on power supplies. You can test this for yourself by running even a simple desktop fan on both type of inverters. On the modified sine inverter you will notice the fan motor gets much hotter while running than it does on pure sine wave. This is because the square portion of the wave form is being absorbed by the windings and some of that is being turned into heat without adding anymechanical energy to the fan itself.

The ironic thing is that from an electronics standpoint, it only costs the manufacturer another 15-20 percent in cost to build pure sine wave versus modified. So there is a large disparity between the two inverter types, which cannot be accounted for in price alone. Now that the chinese are dumping pure sine wave units onto the global market it’s a no brainer. These chinese units cost no more than modified sine wave units, however, they are not built very well. Then again, most of the modified sine wave inverters are not built very well either unless they are well known brands.  Many of the US brands selling modified inverters are now made in China anyways.