What size generator do I need to run a microwave?

A microwave is one of the most common "will it run?" questions, from campers and from people in an outage. The answer depends on one number most people read wrong.

The number that matters: input watts

A microwave has two power figures:

• Cooking power (output): the heat it puts into the food. This is often the big number on the front or the box.
• Input power: what it pulls from the outlet. This is what the generator has to supply.

Input is always higher. Microwaves are only about 50% to a bit over 64% efficient at turning electricity into microwaves, according to Wikipedia's summary of the research. So:

• Formula: input watts ≈ cooking watts ÷ 0.5 to 0.64

Cooking power	Likely input watts
700 W (compact)	about 1,100–1,400
900 W	about 1,400–1,800
1,000 W	about 1,550–2,000
1,200 W	about 1,900–2,400

Check yours. The label on the back or inside the door lists input watts, or amps. Amps × 120 = watts. Use that number, not the table.

What the charts say

Here's what the generator makers' charts list:

• Champion: 600–1,200 W, no extra starting watts
• LCEC: 600 W and 1,000 W models
• Honda: a 625 W microwave at 625 running and 800 starting watts

Honda's figure shows a small start-up bump, so leave a little room. Our calculator uses 1,000 W for a microwave that draws 1,000 W. The calculator above is set to 1,500 W, a middle figure for a microwave sold as 1,000 W cooking power.

What size generator for a microwave?

Microwave input	On its own	With a fridge, lights and Wi-Fi
About 1,000 W	1,200 W+ running	About 1,950 running / 2,900 starting W
About 1,500 W	1,800 W+ running	About 2,550 running / 3,500 starting W
About 2,000 W	2,400 W+ running	About 3,150 running / 4,100 starting W

The "on its own" figures add 20% headroom to the microwave's input watts. The right column adds a fridge (400 running, 1,200 starting), LED lights (100), Wi-Fi (15) and chargers (80), then 20%.

A worked example

The calculator above is set up for this: a microwave drawing 1,500 W, plus the basics.

• Running: 1,500 (microwave) + 400 (fridge) + 100 (lights) + 15 (Wi-Fi) + 80 (chargers) = 2,095 W
• Biggest surge: the fridge, 1,200 − 400 = 800 W
• Starting: 2,095 + 800 = 2,895 W
• With 20% headroom: about 2,550 running and 3,500 starting watts

Will a 2,000 watt generator run a microwave?

Often, yes, but check the running rating. Many "2,000 W" inverters are rated about 1,600–1,900 running watts. Westinghouse's iGen2550DFc, for example, is 1,900 running and 2,550 peak.

• A compact microwave (700 W cooking, about 1,100–1,400 W input): yes, with room for lights and chargers.
• A 1,000 W cooking microwave (about 1,550–2,000 W input): borderline. It may run alone, but not with the fridge starting at the same time.
• A 1,200 W cooking microwave: unlikely on a 2,000 W class unit.

For the rest of what a small unit can run, see what a 2,000 watt generator can run.

Will a 1,000 watt generator run a microwave?

Rarely. A 1,000 W generator's running rating is often below 1,000 W, so check its spec sheet. Only a very small microwave, with a label that shows less than that running figure, has a chance. Don't run anything else.

Tips for cooking on generator power

• Turn off eco mode (idle control) before you start. The engine has to speed up when the microwave kicks on, and eco mode can trip it.
• One heat maker at a time. A microwave, a coffee maker, a kettle or a space heater each use most of a small generator.
• An inverter generator gives cleaner, steadier power, which suits the microwave's electronic controls. See inverter vs conventional generators.

Can a power station run a microwave?

Yes, if its AC output is bigger than the microwave's input watts. A power station rated 1,500 W output won't start a microwave that draws 1,800 W, however big the battery is. Run time is short, too:

• Formula: battery Wh × 0.85 ÷ microwave input watts = hours
• Example: a 1,000 Wh station running a 1,500 W microwave: 1,000 × 0.85 ÷ 1,500 ≈ 0.57 hours, about 34 minutes of cooking

That's plenty for reheating meals during an outage. See power stations for home backup.

Microwave in a camper

RV microwaves are the same story: Champion lists them at 600–1,200 W. On a 30 amp RV, running the microwave and the AC together is the usual way to trip the generator. Run one, then the other. See what size generator for a 30 amp RV.

Safety: Run it outdoors only, 20+ feet from the house, away from windows and doors. Read our carbon monoxide guide.