The Wattage Gap Decides Most of It
An electric blanket runs 60–150W. A space heater runs 1,500W — that's the practical ceiling on a standard 15-amp US circuit, and almost every portable heater sits at it. At 18.4¢/kWh:
- 100W blanket: ~2¢/hour, ~15¢/night, ~$22 per 150-night season
- 1,500W heater: ~28¢/hour, ~$2.21/night, ~$331 per season
Both numbers are ceilings — each device cycles a thermostat rather than drawing continuously — but the ratio holds. The heater costs roughly fifteen times as much to run.
What Each One Actually Buys
The blanket buys you the night. You're stationary, under covers, for 8 hours. That's exactly the window where a deep setback is easiest anyway, and where a blanket removes the last objection to it. It does nothing for the other 16 hours.
The heater buys you a room. You can move around, use a desk, have someone else in there. That's what makes a bigger whole-house setback possible — you're not just tolerating cold, you're relocating the heating. If you work from home in one room while the rest of the house sits empty, this is the case where a heater genuinely earns its running cost.
The trap is running a space heater without setting the rest of the house back. Then you've added $331 of electricity to a heating bill you didn't reduce.
The Fuel Question People Skip
A space heater is 100% efficient at turning electricity into heat, which sounds unbeatable until you compare delivered cost per BTU. At the 2026 US averages of 18.4¢/kWh and $1.70/therm, electric resistance heat costs roughly $53 per million BTU while a 95% gas furnace delivers heat at about $18 per million BTU — gas is around three times cheaper per unit of heat.
So if your central heat is natural gas, a space heater has to overcome a 3× fuel-cost disadvantage before it saves anything. It can — heating one room instead of six is a big enough reduction to clear that gap — but the margin is much thinner than the "100% efficient" framing suggests. If your central heat is a heat pump, the gap is wider still, since a heat pump delivers 2.5–3.5 units of heat per unit of electricity while the space heater delivers one.
Where a space heater looks best: electric resistance central heat (baseboards, electric furnace). There it's the same fuel at the same price, so heating less space is a straight win. Our heating cost by fuel calculator puts every option on the same per-BTU basis.
Safety Differences Worth Knowing
Space heaters are a recognised fire risk in a way blankets largely aren't. Practical rules: plug directly into a wall outlet rather than an extension cord or power strip, keep three feet of clearance from anything combustible, use a model with tip-over and overheat shutoff, and don't run one unattended overnight. A 1,500W heater on a shared 15-amp circuit is also close to the limit — running it alongside other loads on the same circuit trips breakers.
Electric blankets have their own rule set: don't use them with anyone who can't feel heat properly or can't move to adjust the setting, don't tuck them tightly or run them under a heavy mattress topper where heat can build, and replace old units rather than repairing frayed wiring.
The Floors That Apply to Both
Whichever you use, the point is a lower thermostat — and there are limits on how low:
- ~55°F: the usual floor against frozen pipes. Pipes in exterior walls and crawl spaces run colder than the thermostat reads.
- ~60°F: below this, cold surfaces plus normal humidity encourage condensation and mould — the actual failure mode for people who heat only themselves all winter.
- ~64°F: the WHO's suggested general minimum, closer to 68°F with infants, elderly or unwell people in the house.
Our personal heating savings calculator flags these against whatever setting you enter, and is an electric blanket cheaper than heating works through the full season maths.