Best Heat Source for a Power Outage: What Keeps You Warm

A gas furnace makes its heat from gas. The power only runs the blower, the igniter and the control board. That load is small, about 600 W running and about 1,800 W for a second at start.

A furnace blower cycles with the thermostat, about half the time on a cold night, so it averages about 300 W. Take the station's watt-hours x 0.85 for inverter losses and divide by 300. A 1 kWh unit runs it about 3 hours, a 2 kWh unit about 6 hours, and a 4 kWh unit about 12 hours.

A small generator does it all night. The Westinghouse iGen2550DFc runs about 11 hours at quarter load on its 1.1 gal tank. Use an inverter generator, since furnace control boards want clean power.

Most furnaces are hardwired. To power one, an electrician installs an interlock kit and inlet box, or a transfer switch, so you can switch on the furnace circuit. Never backfeed through a dryer outlet. Put a battery CO alarm on every sleeping level and run the generator at least 20 feet from the house.

A 1 lb propane cylinder holds about 21,600 BTU of heat. A full 1 kWh power station holds about 2,970 BTU after losses. One small cylinder holds about 7 times the heat of the battery.

Only buy a heater rated for indoor use with an oxygen depletion sensor (ODS) and a tip-over shutoff. The Mr. Heater Buddy and Little Buddy have both. The ODS shuts the heater off if oxygen in the room drops.

The rules are not optional. Crack a window or door for fresh air as the manual says. Keep a battery CO alarm in the room. Keep 3 feet clear around it. Turn it off before you sleep, and never use an unvented heater in a bedroom. Many building codes ban it.

Never heat a home with a charcoal grill, a gas grill, a camp stove, a gas oven or a generator. They make carbon monoxide fast, and CO kills people every winter outage.

A blanket heats you, not the room, and that is why it lasts so long on a battery. A typical electric blanket draws about 100 W on high and cycles about half the time, for an average of about 50 W.

The math is capacity x 0.85 / 50. The 1,024 Wh BLUETTI Elite 100 V2 gives about 17 hours, the 1,070 Wh Jackery Explorer 1000 v2 about 18 hours, and the 2,074 Wh Elite 200 V2 about 35 hours. Two blankets halve those numbers.

Plug the blanket straight into the power station. Sunbeam says not to use an extension cord or power strip. A 12V blanket plugs into the station's car outlet and skips the inverter, so more of the battery goes to heat. A heated mattress pad works the same way and keeps the heat under you.

A 1,500 W heater on a 1 kWh station lasts about 35 minutes flat out. The 1,024 Wh Elite 100 V2 has about 870 Wh usable, and 870 / 1,500 = 0.58 hours. With the thermostat cycling it at 60 percent, you get about 1 hour.

That same charge runs an electric blanket for about 17 hours. Even a 6 kWh home battery runs a 1,500 W heater only about 6 hours with cycling. A space heater only makes sense on a generator.

See the full table for 1, 2, 4 and 6 kWh units in our guide on how long a power station runs a space heater.

Gas furnace and a generator budget: a dual fuel inverter generator, an interlock kit and a battery CO alarm. The Westinghouse iGen2550DFc is $500 to $1,000.

Gas furnace, no generator: a 2 kWh power station hooked to the furnace circuit by an electrician, about 6 hours of blower per charge. Around $899.

Electric heat or no hookup: a Mr. Heater Buddy and a CO alarm for the day, and an electric blanket on a 1 kWh power station for the night. The Mr. Heater Buddy is under $100, the Kidde alarm under $100, the Sunbeam blanket $100 to $250, and a BLUETTI Elite 100 V2 station about $499.

Apartment: an electric blanket on a power station. No flame, no fumes, no noise.