GeneratorSizer

Which generator is right for me?

Published October 3, 2026.

Built by Jeremy Panasuk.

The right class is the one that clears your list. The path below starts at 2,000 W and only leaves that class when a published row forces it.

Quick answer: Honda's Energy Star fridge at 192 W running / 1,200 W start, plus a 1/3 hp furnace fan at 700 W running / 1,400 W start, marked 240 V, sizes to 2,000 W. That is a portable recommendation. It is not a 20 kW standby. Add a 4-ton air conditioner at the top of Champion's band and the same formula leaves the 2,000 W class. Enter the rows on the calculator before you shop.

The list that is actually 2,000 W

Honda marks that furnace-fan row 240 V. A 120 V inverter can cover the fridge's 1,200 W start and still miss the fan, because the fan is not a 120 V load on Honda's chart. The fridge alone, without the fan, is the 1,500 W case on generator vs battery backup. Gasoline at 50% of this 2,000 W recommendation lasts 14.0 hours on a 4 gallon tank. Propane at 1.37 times the gasoline rate lasts 10.2 hours on the same 4 gallons. Those fuel lines are the home calculator, walked on how much propane a generator uses.

If you will not run the fan and the fridge's compressor start in the same moment, the load sequencer is the other tool. It uses the same highest-start extra as the home calculator, then stages rows into always, wait, and never-overlap. The 2,000 W figure above is the home calculator, with both rows on.

Branches that change the class

You are only keeping food cold and a few small 120 V loads. Stay with the fridge page and the camping list. A fan, a laptop, and a radio size to 1,000 W on best portable generator for camping. A battery with a published watt-hour rating, matched to the same 192 W fridge, is on best solar generator. That page is one sheet, not a test.

You want the furnace fan, and it is the 240 V row. The generator needs 240 V output. The watt recommendation is still 2,000 W until you add more rows. A transfer switch is required if those loads are on household circuits. Cord-versus-switch is on backup generator installation.

You want central air. Champion's 4-ton row, at the top of the band, plus the fridge, sizes to 10,000 W on 10 kW generator for a home. The peak is 8,192 W. Adding Honda's 4,500 W water heater moves that page to 15,500 W. Do not keep the 2,000 W answer once the condenser is on the list.

You are away when the power fails, and you want the set to start itself. That is a standby, not a bigger portable of the same 2,000 W. The watts still come first. One dryer-plus-4-ton-plus-fridge list sizes to 16,500 W and is compared with Generac's 20,000 W LP / 18,000 W natural-gas ratings on 20 kW home standby. Portable versus automatic, as an install choice, is on portable vs standby.

The tools are a saw and a washer, not a house. Honda's 10-inch table saw and 1 hp pressure washer size to 7,000 W on how to size an industrial generator. A building service is the point where that page tells you to stop and hire an engineer.

You are above 1,000 feet, or the set will sit near a property line. Derate is a separate step from the watt recommendation. The script's thresholds are on altitude derate. A published decibel rating and the distance formula are on noise at the lot line. Neither tool changes the 1,592 W peak. They change whether a nameplate that looked large enough still is, and whether the neighbor's lot line is the constraint.

A common mistake

Buying a 20 kW standby because a neighbor did, while the list in front of you is a fridge and a furnace fan. Those two rows are a 2,000 W recommendation. The 20 kW sheet is the right comparison only after the load list, the 240 V loads, and the wish for automatic start are actually on the table. The other mistake is dropping the furnace fan's 240 V mark and shopping a 120 V inverter whose watt rating happens to say 2,200.

Limits, and when to call a pro

Nameplates beat chart rows. If the fan motor is not the 1/3 hp row, do not keep 700 and 1,400. Re-enter the plate on the calculator. Connecting any of these sets to a panel takes a licensed electrician and a permit where local code requires one. Outdoors, at least 20 feet from the house, is still the portable rule on how to run a generator safely. An outage sequence for the first hours, food in a closed fridge, and what to do when utility power returns is on how to use a generator when the power goes out.

Compiled with AI assistance from the sources below. Spot an error? Email [email protected].

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