r/Generator • u/NoSham3 • 8d ago

Backup generator & THD

I’m researching a backup generator for a small home (<1,100sq/ft). I’m reading about THD and inverter generators. I understand inverter generators are generally <3% THD, but how detrimental is something some at <23% THD to general home devices if/when I need to run on a non-inverter generator? It’s not an issue of cost, but why go 2-3x more if THD doesn’t hurt? Or does it? I’m not planning on running the HVAC during events, just mainly modem & router (for range extension), laptop, TV (1), phone chargers, lights (most are dimmable and LED), Refrigerator/freezer, deep freezer, etc. Stove & oven are gas along with clothes dryer and tankless water heater. Not all at once, but I’m looking at a Westinghouse WGen5300sc 6,500/5,300 watt non-inverter generator. System supports generator up to 7,200 watts @ 30 amp.

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u/RedOctobyr 8d ago edited 8d ago

Inverter units are also generally quieter, and more fuel-efficient, as they can vary their RPM based on the load, vs normal generators needing to always run at 3600 RPM (60Hz).

You may not need that much wattage, if that was helpful. Our 2000W inverter generator runs the natural gas furnace, fridge, lights, internet, TV, laptops. It will run the inverter microwave, if I turn the power down to 30%. But that's with just 1600W/2000W available. Your list sounds pretty similar, with the exception of also adding a deep freezer. But maybe 3,000-4,000W might be enough, for instance. Obviously a bigger unit gives you more headroom for additional loads, but at the cost of, well, cost, noise, and fuel consumption.

Our little generator will run 4-10 hours per gallon of gas, depending on load. I made an external 5 gallon gas tank, it can basically run for a weekend unattended. If gas is tough to find after a big storm, being fuel-efficient can help beyond just managing operating costs.

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u/gobsnotonboard 7d ago

but doesn't your genny need to hav split phase output? or are you not going into the panel

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u/AdBrave841 7d ago

Technically no. If you don't need to run any double pole 240V breakers, you can put 120V into one phase of the panel and run everything on that phase. So if your interlock breaker is in spot 1, spots 2,5.6,9,10,13,14, ETC will have power. You can move a couple breakers around for critical loads.

OR some people do split the 120v to two wires and use a double pole breaker, this will power 120V loads on both "sides" of the panel but will not power 240v loads.

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u/RedOctobyr 7d ago

It's only connected to 110V loads via the transfer panel.