The Fundamental Rule: Fuel Cost per BTU

Natural gas delivers heat at roughly $0.04–$0.06 per kWh-equivalent at current U.S. prices. Electric resistance heating costs $0.13–$0.25 per kWh. A 1,500W space heater is electric resistance — it costs 3–5x more per BTU than a gas furnace. This is the core reason space heaters rarely save money vs. gas heat: you're substituting cheap fuel with expensive fuel.

Heat pumps change this math. A heat pump delivers 2–4 kWh of heat per kWh of electricity consumed (COP 2–4), making it cost-competitive with or cheaper than gas. A space heater is COP 1 — it delivers exactly 1 kWh of heat per kWh consumed. So space heaters don't save money vs. heat pumps either.

When Space Heaters Do Save Money

The math works when: (1) you use the space heater in one room only, (2) you drop the central thermostat by at least 5–8°F, and (3) the savings from reduced central heating exceed the heater's electricity cost. This happens most often in large homes with gas heat where the per-room heating cost is high, and in homes where one person works from home all day in a single room. See our detailed guide: How Much Does It Cost to Run a Space Heater?

The Zone Heating Strategy

Zone heating — heating only occupied spaces — is the legitimate use case for space heaters. If your home has 4 rooms and you're only in 1, heating the other 3 to 70°F wastes energy. Dropping central heat to 60°F and supplementing with a space heater in the occupied room can save $30–60/month in a large gas-heated home. The key: the thermostat must actually go down. Running both at the same temperature always costs more. Use our Space Heater Cost Calculator to model your exact numbers.

Electric Homes: The Exception

For homes with electric baseboard or resistance heating, the cost-per-BTU is the same whether from baseboards or a space heater. In this case, using a space heater in one room and turning off baseboards in other rooms does save money — you're just concentrating the same fuel type rather than switching. The savings come from heating less square footage, not from any efficiency difference in the heater itself.