Therms to kWh converter
1 therm is 29.31 kWh. Type in either box; handy for US gas bills and British wholesale prices.
1 therm = 29.31 kWh (105.506 MJ, 100,000 BTU)
Why 29.31?
A therm is 100,000 British thermal units (BTU). A BTU started out as the heat that warms a pound of water by one degree Fahrenheit. Today it's fixed at about 1,055 joules, and the therm is defined as exactly 105.506 MJ. Divide by 3.6 and you get 29.31 kWh.
Strictly, NIST lists two therms: the European one (105.506 MJ) and a US one (105.480 MJ). In practice US utilities simply use 100,000 BTU. The difference is under 0.03%, too small to show on any bill.
US gas bills often count in therms, and some utilities bill in Ccf, which is 100 cubic feet of gas. British household bills switched to kWh, but wholesale gas in Britain still trades in pence per therm.
On the napkin
Say a US home burns 60 therms of gas in a cold month. That's 60 × 29.31 = 1,758 kWh.
Prices go the other way, so you divide: say wholesale gas costs 100p a therm. That's 100 ÷ 29.31 = 3.4p per kWh, before anyone adds network costs, VAT and the rest.
Common values
| Therms | kWh |
|---|---|
| 1 | 29.31 |
| 10 | 293.1 |
| 100 | 2,931 |
| 1,000 | 29,307 |
| kWh | Therms |
|---|---|
| 1 | 0.0341 |
| 100 | 3.41 |
| 1,000 | 34.12 |
| 10,000 | 341.2 |
Need another unit?
The full energy converter shows any amount in every energy and power unit at once, from joules to kilowatt-hours to cups of tea.
Want to know what your gas bill would be with a heat pump?
The free spreadsheet works it out from the prices on your own bill. It comes by email, together with the unit converter as a sheet. One short email a month at most.
Send me the spreadsheetsSources: therm (EC) = 1.05506 × 10⁸ J and therm (US) = 1.054804 × 10⁸ J, NIST Special Publication 811, Appendix B. 1 kWh = 3.6 MJ by definition.
Spot a mistake? Email [email protected] and I'll fix it.