A gas furnace still needs electricity during an outage. The burner may use gas, but the blower motor, controls and ignition need power. The two numbers that matter most are blower running watts and motor startup demand.
Enter your furnace watts and outage plan in the Backup Power Map →
How much power does a gas furnace need?
There is no safe one-number answer for every furnace. Blower size, ECM vs PSC motor, speed and installation all change consumption. Use the furnace nameplate, blower motor label or manufacturer documentation when available. The WhenGridFails calculator includes a screening estimate for a 1/2 HP blower but lets actual watts override it.
Why startup surge matters
A battery can have enough watt-hours for the night and still fail to start a motor. Compare both continuous AC output and verified startup capability. Do not treat a marketing “power lifting” mode for resistive appliances as proof of motor-start capability.
How much battery for an overnight outage?
Runtime depends on how long the blower actually runs, not simply the number of hours you want heat available. Colder weather, thermostat setting, insulation and furnace cycling change daily energy use. Estimate running watts × expected blower run time, then allow for inverter losses and reserve.
Connection is part of the decision
Many furnaces are hardwired. A portable power station cannot simply be plugged into the furnace unless the installation provides an approved connection method. Never backfeed household wiring. Have a qualified electrician confirm the transfer or furnace connection method.
What size power station should you consider?
For modest verified 120V furnace loads, start by comparing the calculated continuous output, startup requirement and watt-hours against 1–2kWh-class systems. For more runtime, expansion-capable systems can be useful. See EcoFlow DELTA 2 Max vs BLUETTI AC200L for a 2kWh-class comparison.
Check BLUETTI AC200L price & availability →
Affiliate disclosure: WhenGridFails may earn a commission at no extra cost to you. Technical load fit comes first.
Before you buy
Record furnace voltage, blower running watts/amps, motor type, startup requirement if published, connection method, expected outage duration and whether solar or another recharge source will be available.