Therms to kWh Converter
| Therms | kWh | The amount |
|---|---|---|
| 1 | 29.31 | the billing unit itself |
| 10 | 293.07 | a mild month of hot water |
| 50 | 1,465.33 | a light heating month |
| 100 | 2,930.66 | a cold-winter month, family home |
| 400 | 11,722.63 | a whole heating season, gas-heated home |
Gas bills are priced in therms and electricity bills in kilowatt-hours, so the only honest way to compare a gas furnace with a heat pump is to convert one side to the other. The bridge runs through heat units: one therm is exactly 100,000 Btu, one kilowatt-hour is 3,412 Btu per the EIA's conversion tables, and dividing gives about 29.31 kWh per therm.
Type a number from either bill and the converter shows the other side. The comparison that follows is where the money is: one therm of gas heat costs whatever your gas rate says, but a heat pump delivers the same heat for roughly a third of the raw electricity because it moves heat rather than making it - so 29.31 kWh of resistance heating matches one therm, while a typical heat pump needs closer to a third of that. Which one wins in dollars depends on your two rates, and now you can line them up.
How to use
- Type therms from your gas bill to see the kWh equivalent, or kWh from an electric quote to see the therm side.
- For appliance comparisons, remember direction: 1 therm of heat = 29.31 kWh of resistance electric, but a heat pump multiplies its electricity.
- Compare dollar bills, not units: gas price per therm against (kWh price x kWh needed) - the converter gives you the kWh needed.
Frequently asked questions
What exactly is a therm?
One therm is 100,000 British thermal units - a hair less than the energy in burning 100 cubic feet of natural gas, which is why old gas bills sometimes quote Ccf instead. Utilities standardized on the therm because it prices the heat delivered, not the volume, and it survives on every US gas bill as the billing unit the EIA's tables define as exactly 100,000 Btu.
How many kWh is one therm?
About 29.31 kWh - the division of 100,000 Btu per therm by 3,412 Btu per kilowatt-hour, the two factors in the EIA's energy conversion tables. Working the other way, one kWh is about 0.034 of a therm. Keep the pair in mind as 'a therm is roughly thirty kilowatt-hours' and every home-energy comparison gets one step easier.
Does a heat pump really use a third of the electricity?
A resistance heater turns one kWh of electricity into exactly one kWh of heat, so it needs the full 29.31 kWh to match a therm. A heat pump moves existing heat instead, delivering around three units of heat per unit of electricity in moderate weather - call it 10 kWh to match a therm - with the multiplier shrinking in deep cold. That coefficient is the whole economic argument, and it is why the comparison belongs in kWh, not therms.
Why do gas and electric bills use different units?
History and physics: gas utilities have billed by heat content since gas lights gave way to gas heat, and the therm made sense of a fuel whose energy per cubic foot varies by source. Electricity was always metered in kilowatt-hours because that is what the meter measures directly. Neither unit is wrong - they are just fluent in different centuries, which is what this converter is for.
How do I compare my gas bill with a heat-pump quote?
Convert your winter gas use to kWh with the tool - say 400 therms becomes about 11,700 kWh of heat - then divide by the heat pump's expected efficiency (around 3 in moderate climates) to get the electricity it would actually buy: near 3,900 kWh. Price that at your electric rate and compare against your gas bill. The honest version includes the winter efficiency drop and your utility's fixed charges.