Running a Furnace on a Power Station During a Winter Outage

When the power goes out in January, the furnace stops — not because it’s out of gas, but because the blower fan, igniter and control board all need electricity. A portable power station can keep them running, and it doesn’t create the carbon monoxide risk of a fuel generator. Here’s how to do it properly.

Step 1: Find out what your furnace draws

Open the furnace’s front panel and look for the nameplate sticker. You’re looking for the blower motor’s rating, usually in amps (A) or full-load amps (FLA). Multiply amps by 120 to estimate watts. A blower rated at 4 A draws roughly 480 W while it’s running.

Two things change the picture:

• Motor type. Older furnaces often have PSC motors that draw several hundred watts. Newer high-efficiency furnaces often have ECM (variable-speed) motors that draw much less, especially at low speed.
• Cycling. Your furnace doesn’t run the blower nonstop. On a very cold night it might run half the time or more; on a milder night, much less.

Step 2: Size the power station

You need two things:

1. Enough output (watts) to handle the blower’s startup surge plus anything else running at the same time. For most furnaces, 1,500 W or more gives comfortable headroom.
2. Enough capacity (watt-hours) to last as long as you need. A blower averaging 225 W over its on-off cycle uses about 225 Wh per hour — plus inverter losses.

Plug your numbers into the winter runtime calculator. It shows how long each model would last with your loads.

Step 3: Connect it safely

This is the part not to improvise.

• Plug-in furnaces: some furnaces connect with a regular plug. If yours does, you can plug it into the power station.
• Hard-wired furnaces (most of them): you need a transfer switch or a dedicated inlet installed by a licensed electrician. This lets you disconnect the furnace from the grid and power it safely from the power station.
• Never backfeed. Plugging a power station into a wall outlet with a “suicide cord” to power house circuits is illegal in many places, can damage equipment, and can electrocute utility workers repairing the lines.

Step 4: Keep the power station warm

Put the power station inside the heated part of the house, not in the garage. Most lithium power stations won’t charge below 0°C, and some stop working at around −10°C. See the limits for each model in our cold-weather spec database.

Stretching your runtime

• Lower the thermostat a few degrees — the blower cycles less.
• Close off rooms you don’t need to heat.
• Run the fridge on the same power station only if you have capacity to spare; a well-sealed fridge stays cold for hours unplugged.
• If power returns briefly, recharge immediately.

Which power station?

Our pick for furnace backup is the EcoFlow DELTA 3 Plus for its output and expandable capacity. See all our options in best power stations for a winter power outage.