kWh cost converter
Electricity in kilowatt-hours, gas in therms or megajoules, a heater rated in Btu: put any of them on the same scale, with the price alongside.
Cost
$42.50
250 kWh at $0.17 per kWh
That amount of energy is
- watt-hours
- 250,000 Wh
- kilowatt-hours
- 250 kWh
- megajoules
- 900 MJ
- British thermal units
- 853,035 Btu
- therms (U.S.)
- 8.53239 therm
That price is
- per kWh
- $0.17
- per MJ
- $0.0472
- per therm
- $4.98
- per million Btu
- $49.82
Estimates from the figures you enter: not a bill, and not financial advice.
Energy is energy, whatever the unit
Electricity is billed in kilowatt-hours, gas often in therms or megajoules, and heating equipment is rated in Btu. They all measure the same thing, so any amount converts exactly. One kilowatt-hour is 3.6 megajoules by definition; NIST gives one Btu as 1,055.056 joules and the U.S. therm as 105.4804 megajoules.
Prices convert the other way round: because a kWh is 3.6 MJ, a price per kWh is 3.6 times the price per MJ. That puts an electricity rate and a gas rate on the same footing, before you allow for how efficiently each appliance turns its fuel into heat.
1 kWh = 1,000 Wh = 3.6 MJ ≈ 3,412.14 Btu ≈ 0.0341 therm
Cost = energy in the price's unit × price
Sources
- NIST, NIST Guide to the SI, Appendix B.9: kilowatt hour = 3.6 MJ (exact); British thermal unit (IT) = 1.055 056 kJ; therm (U.S.) = 105.4804 MJ (exact); therm (EC) = 105.506 MJ.
Questions
Is a kWh the same as a kW?
No. A kilowatt is a rate of use (power); a kilowatt-hour is an amount (energy), one kilowatt for one hour. A 2 kW heater running for 3 hours uses 6 kWh.
Why compare gas and electricity prices per kWh?
It shows what the energy itself costs. A gas boiler loses some heat up the flue, so divide a gas price by the boiler's efficiency before comparing it with an electric heater.
Which therm does this use?
The U.S. therm, 105.4804 MJ, as listed by NIST. The EC therm used in Europe is about 0.02% larger, too little to matter on a bill.