Electric Heating Cost Calculator

Heating a space electrically can be cheap or expensive depending on whether you are using resistance heat (100% efficient but costly per BTU) or a heat pump (200-400% efficient because it moves heat rather than generating it).

Heat load calculation

The simplified heat load formula for residential spaces:

BTU/hour = room area (sq ft) x ceiling height (ft) x 0.133 x delta T (F) x insulation factor

Insulation factors: poor (old home, single-pane windows) = 0.20, average = 0.15, good (modern, well-insulated) = 0.10.

The constant 0.133 accounts for the thermal properties of a typical wall assembly. This is a rough estimate — a proper Manual J calculation by an HVAC engineer considers window area, infiltration, duct losses, and climate data.

Efficiency and COP

Electric resistance heaters (baseboard, plug-in space heaters): 100% efficient. Every watt in becomes one watt of heat.

Heat pumps: A coefficient of performance (COP) of 2.5-4.0 means for every watt of electricity consumed, you get 2.5-4 watts of heat. A COP of 3 means 300% effective efficiency.

kWh/hour = (BTU/hr) / 3,412 / (efficiency/100)

Daily cost = kWh/hour x run_hours x electricity_rate

Space heater reality check

A 1,500 W space heater run flat out for 8 hours uses 12 kWh, which is $1.92 at the current US average of about $0.16/kWh, or roughly $58 a month. For one room that is frequently more than heating an entire house with gas.

That figure is deliberately the worst case: a heater at full power the whole time. The calculator above works from the heat the room actually loses, so a well-insulated room with a modest temperature difference needs the heater on only part of the time and costs a good deal less. The two numbers bracket the real answer.

Resistance heat is convenient and cheap to buy, and that is the whole of its case. Per unit of heat delivered it is the most expensive option on the market outside of a few hydro and solar-rich regions. It earns its place as a supplement, warming the room you are actually sitting in while the rest of the house runs cooler, rather than as a primary heat source.

What this estimate covers

The heat load here is a rough single-room figure. It assumes a typical amount of exterior wall and window for the floor area, and it does not know about a draughty door, an uninsulated floor over a crawlspace, or a south-facing window doing useful work on a sunny afternoon. Treat it as an order of magnitude, and note that a room with two exterior walls can easily need half again as much as one with a single outside wall.