Electric Heating Cost Calculator

How it works

An electric resistance heater turns every kilowatt-hour it draws into 3,412 BTU of heat: its coefficient of performance (COP) is 1. A heater's cost is therefore its kilowatts times the hours it runs times your rate. If you start from the heat you need in BTU/h, the calculator converts it to the watts a resistance heater would draw.

A heat pump moves heat from outdoors instead of making it, so it delivers COP times as much heat as the electricity it uses. The same BTUs from a heat pump at COP 3 cost a third as much as from resistance heat. The season difference is the resistance cost times (1 − 1 ÷ COP).

Cost per million BTU puts electricity on the same footing as other fuels: one million BTU is 293.07 kWh, so at COP 1 it costs 293.07 × your rate, and at a higher COP proportionally less.

Formula

W (BTU/h mode)    = BTU/h ÷ 3.41214
BTU/h delivered   = W × 3.41214
resistance kW     = W ÷ 1,000;   heat pump kW = resistance kW ÷ COP
cost per hour     = kW × rate ÷ 100
cost per day      = cost per hour × run hours per day
cost per season   = cost per day × heating days
season difference = resistance season × (1 − 1 ÷ COP)
cost per MMBTU    = 1,000,000 ÷ 3,412.14 × rate ÷ 100 ÷ COP   (COP 1 for resistance)

Example

A 1,500 W heater delivers 5,118 BTU/h. Running 8 hours a day at 18 ¢ per kWh it costs $0.27 an hour, $2.16 a day and $324.00 over a 150-day season.

A heat pump at COP 3 delivering the same heat draws 0.5 kW: $0.09 an hour, $0.72 a day and $108.00 a season, $216.00 less. Resistance heat costs $52.75 per million BTU at 18 ¢; the heat pump at COP 3, $17.58.

Assumptions and limitations

• Resistance heat converts all electricity to heat in the room (COP 1). A heat pump's COP is an input you choose and is held constant; real COP falls as the outdoor temperature drops and includes defrost and backup-heat losses, so a single seasonal figure is an approximation. The COP ranges shown are typical values.
• Run hours are the hours the heater or compressor actually runs, not the hours the thermostat is set to heat.
• The rate is a single flat price per kWh; the 18 ¢ default is illustrative. Tiered and time-of-use tariffs, fixed charges and taxes are not modelled.
• The heat-pump figure prices the same delivered heat; it is not a sizing or selection calculation, and the cost of buying or installing equipment is not included.
• 1 kWh = 3,412.14 BTU (IT BTU; EIA rounds to 3,412).

Frequently asked questions