Some postings on DIY caution about using square waves and dirty sine waves to power some electronic equipment.

Which whole house generators generally put out clean sine waves? (I looked on the official Briggs and Stratton website and found nothing on this topic.)

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    You'll have to provide specific model numbers - there are cheap "contractor specials" repackaged as home standby generators, and there high quality (typically diesel) generators. So yes, you can get a nice $10,000 diesel whole house generator that puts out a very stable wave form, but you can also get whole house generators that are no better than the $750 7500W contractor generator you can buy at the local home improvement store. And there's a whole spectrum in between. – Johnny Dec 22 '15 at 18:24
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    Down voting because there is no specific answer to this. As @Johnny said, it will depend on the specific generator. – Steven Dec 22 '15 at 18:50
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    Voting to close as a shopping question; goes out of date too quickly to be a good SE question, and frankly you canresearch it as easily as we can. – keshlam Dec 24 '15 at 3:54

As others have said, this will vary considerably from one device to another.

One way to measure the quality of electricity is "Total Harmonic Distortion" (THD), which is a measure of how much distortion from a true sine wave there is. A perfect sine wave is 0%, and a square wave (very poor) is 48%. Anything under 5% is generally considered "perfect" for household usage, and a good generator should be around that. But a cheaper generator could be 20-30% +. You may have to do some digging to find the specs for a model since not all manufacturers advertise it prominently.

Frankly, it's hard to tell whether your home devices will be troubled by high THD or not. It's not nearly as simple as "electronics"... most electric devices today have a DC converter to supply the device with low-voltage DC power, and actually are pretty isolated from the mains power. I think most DC power adapters are pretty tolerant of poor power, wide voltage ranges, wide frequency ranges, etc.

Note that there are other factors that may vary, like AC frequency (in the US that should be 60 Hz with very little variation), voltage (in the US should be between 110V and 130V for single-phase or 220V-260V for split-phase).

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    Computer power supplies (especially PFC ones) are actually pretty picky about power quality. I tried to run a remote site off of generator, the computers were pretty unreliable on small gas powered generators up to 7.5KVA, but worked pretty well with a 6000KVA inverter generator, and with a 15KVA diesel standby generator. We ended up putting an "online" UPS in front of the computers to help with power quality problems, line-interactive UPS's just passed most of the bad power to the computers. – Johnny Dec 24 '15 at 0:14
  • @Johnny: I think it really depends on the particular device. At my office we have plenty of PCs on modified-sine-wave UPSs without incident. Also most laptop chargers are compatible with virtually any power source. – Hank Dec 25 '15 at 17:54
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    A few minutes of runtime when a modified sinewave UPS fails over to battery is not likely to cause any problem (as long as the UPS can handle the inrush current of a PFC power supply), but running them for a few hours or days on a standby generator is a different story, and based on my experience on running an office on generator power, you'll get spontaneous reboots and other glitches throughout the day. – Johnny Dec 25 '15 at 19:54

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