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Comment on Connecting a Portable Generator to the Home Main Electric Panel

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I recently paid an electrician to do the exact work discussed in the article on my home in Austin, TX. Total cost for installation of the inlet, 50 amp breaker, and interlock kit as well as a 25 foot heavy duty cable with 6-50P that hooked my generator up to the inlet was about $1K.

A 8500W sustained 11000W surge generator from Northern Tool that’s enough to power my whole house for 3 days or so with two 5 gallon jerry cans was another $1300.

If you do go generator shopping, sizing is important, but it’s also important to look for a generator with low Total Harmonic Distortion (<5%) if you plan to use it in your house else your sensitive electronic devices may be damaged. Surprisingly, a large majority of generators on the market, including the ones sold by Costco, don’t have low THD. GeneratorBible website is a good resource for comparison shopping and education.

We mainly made the purchase for peace of mind after last year’s “incident” (even knowing that it was a once in 30 year storm).

Transfer switches are another alternative, but are more expensive and can only handle the 4-6 breakers you assign to them. Interlock kits can use any breaker. So at higher expense you get less functionality in exchange for a solution that is slightly more foolproof.

generator with low Total Harmonic Distortion

With any electronic device built after the 90's, this will not be an issue. Everything that uses a switched mode power supply doesn't care about the waveform.

The waveform shape will likely only affect devices from before the 90's with inductors trying to do clever things, such as florescent lights.

With a very poor waveform, classical induction motors will run hotter. That includes fridge compressors and fans in furnaces, pumps in dishwashers, etc. I doubt any will fail though - they normally have a decent thermal margin.

Do you happen to have a citation for this, by chance? I didn't come across any good literature demonstrating how THD affects different types of devices during my research. Only that it was not recommended for usage on things like televisions, laptops, and other "sensitive" electronic devices.

Note that generators are not designed to be used indoors, and are likely to lead to major health risks and even death if you do so. Not even in your garage.

Be careful out there!

Yes, I realize now that my comment could have been interpreted as actually running the generator inside. NEVER do this. Outside only. What I meant to say in a more clear way is that if you intend to use the generator to power items inside your home that you should use a generator with low THD unless you are only using your generator for something like operating a heater or furnace.

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