Key numbers
- 1 kWh = 3,412.14 BTU (International Table BTU)
- 1 therm = 100,000 BTU ≈ 29.31 kWh
- 12,000 BTU/h = 1 ton of cooling = 3.52 kW of heat
- 1 BTU ≈ 1,055 joules; 100,000 BTU ≈ 105.5 MJ
On this page
- How to use the BTU to kWh
- How to convert BTU to kWh
- BTU to kWh conversion table
- BTU/h equipment ratings in kW
- kWh to BTU: when you need it
- Tips for using BTU conversions
- Where BTU, therms and kWh appear
- History of the BTU
- References
- Step-by-step: compare a gas bill with an electric bill
- Frequently asked questions
How to use the BTU to kWh
- 1Enter your numbersFill in energy (BTU) and or a heating/cooling rating (BTU/h). Every field starts with a typical value you can overwrite.
- 2Check the assumptions1 kWh = 3,412.14 BTU. One therm of natural gas = 100,000 BTU ≈ 29.31 kWh. A 12,000 BTU/h air conditioner (1 ton) moves 3.52 kW of heat, but draws far less electricity.
- 3Read the resultsThe calculator shows kilowatt-hours, therms, megajoules and 12,000 btu/h as power, and updates as you type.
- 4Use the resultCompare it with your bill, a quote or a product spec sheet before you buy or install anything.
Results update as you type. Back to the calculator ↑
This BTU to kWh converter translates British thermal units, the unit used for gas bills, furnaces and air conditioners, into kilowatt-hours, the unit on your electric bill. It also gives therms and megajoules, and converts a BTU/h equipment rating into kilowatts and tons of cooling.
How to convert BTU to kWh
A British thermal unit (BTU) is the heat needed to raise one pound of water by one degree Fahrenheit (EIA). The International Table BTU is defined as 1,055.056 joules (NIST SP 811 Appendix B), and 1 kWh is 3,600,000 joules, so:
- kWh = BTU ÷ 3,412.14
- BTU = kWh × 3,412.14
- Therms = BTU ÷ 100,000
- kWh = therms × 29.31
- kW = BTU/h ÷ 3,412.14, and tons = BTU/h ÷ 12,000
Worked example with the default values
- Energy: 100,000 BTU
- kWh: 100,000 ÷ 3,412.14 = 29.307 kWh
- Therms: 100,000 ÷ 100,000 = 1 therm
- Megajoules: 100,000 × 0.00105506 = 105.506 MJ
- Equipment rating 12,000 BTU/h: 12,000 ÷ 3,412.14 = 3.517 kW, or 1 ton
BTU to kWh conversion table
| BTU | kWh | Therms |
|---|---|---|
| 1 BTU | 0.000293 kWh | 0.00001 |
| 1,000 BTU | 0.293 kWh | 0.01 |
| 3,412 BTU | 1.0 kWh | 0.034 |
| 10,000 BTU | 2.931 kWh | 0.1 |
| 50,000 BTU | 14.654 kWh | 0.5 |
| 100,000 BTU | 29.307 kWh | 1 |
| 1,000,000 BTU | 293.07 kWh | 10 |
BTU/h equipment ratings in kW
| Rating (BTU/h) | Kilowatts | Tons of cooling |
|---|---|---|
| 5,000 | 1.47 kW | 0.42 |
| 9,000 | 2.64 kW | 0.75 |
| 12,000 | 3.52 kW | 1 |
| 24,000 | 7.03 kW | 2 |
| 36,000 | 10.55 kW | 3 |
| 60,000 | 17.58 kW | 5 |
| 100,000 | 29.31 kW | 8.33 |
kWh to BTU: when you need it
Going the other way helps when you compare electric and fuel heating. A 1,500 W space heater running one hour uses 1.5 kWh and puts 1.5 × 3,412.14 = 5,118 BTU of heat into the room. Electric resistance heat turns all of its electricity into heat. A heat pump moves more heat than it uses, which is why the cooling or heating rating of an AC or heat pump is much larger than its electrical draw.
Tips for using BTU conversions
- Read labels carefully. Equipment often says “BTU” when it means BTU per hour.
- Account for efficiency. A therm of gas burned in a furnace delivers less useful heat than 29.31 kWh, depending on the furnace efficiency rating. Compare useful heat delivered, not fuel energy alone.
- Gas bill units. If your bill uses CCF rather than therms, the utility’s heat-content factor converts between them, or use the EIA energy conversion calculators.
- Rounding. 3,412 and 3,413 both appear in older references; the difference is under 0.1%.
Pro tip
To convert heating power ratings to other units, try the kW to watts converter. To work out what an electric heater or AC costs to run, use the electricity cost calculator, and for the basics of energy units read what is a kilowatt-hour.
Where BTU, therms and kWh appear
- Natural gas bills list therms or CCF. Multiply therms by 29.31 for kWh of fuel energy.
- Furnaces and boilers are rated by input and output in BTU/h. The output rating is the useful heat.
- Air conditioners and heat pumps are rated in BTU/h of cooling or heating, and in tons (12,000 BTU/h each).
- Propane and heating oil are sold by the gallon, and suppliers or the EIA publish their BTU content per gallon, so you can convert a fuel delivery to kWh with this tool.
- National energy statistics from the EIA are often reported in quadrillion BTU (“quads”), which makes BTU the common unit for comparing coal, gas, oil, nuclear and renewables.
History of the BTU
The BTU grew out of 19th-century steam and heating engineering, when heat was measured by warming a pound of water by one degree Fahrenheit. In a short 1942 note in Nature, G. Woledge traced its history and observed that the name “British thermal unit” apparently originated in the United States before being adopted in Britain (Woledge 1942). Because the heat capacity of water changes slightly with temperature, several BTU variants existed; the International Table value of 1,055.056 J, used in this calculator and listed in NIST SP 811, ties it to the joule. The BTU remains the standard US unit for comparing fuels in national energy statistics (EIA).
References
- Woledge, G. (1942). “History of the British Thermal Unit.” Nature, 149, 613. doi:10.1038/149613c0
- Thompson, A. & Taylor, B. N. (2008). Guide for the Use of the International System of Units (SI). NIST Special Publication 811. doi:10.6028/NIST.SP.811e2008
Step-by-step: compare a gas bill with an electric bill
- Read the therms used on the gas bill.
- Multiply by 29.31 to get kWh of gas energy.
- Divide the gas bill amount by that kWh to get a price per kWh of fuel.
- Compare it with your electricity price per kWh, after allowing for furnace efficiency or heat pump performance.
FAQ
Frequently asked questions
How many BTU are in a kWh?
One kilowatt-hour equals 3,412.14 British thermal units, based on the International Table BTU of 1,055.056 joules. Many references round it to 3,412 BTU. To convert kWh to BTU, multiply by 3,412.14.
How do I convert therms to kWh?
One therm is 100,000 BTU, so multiply therms by 29.31 to get kWh. A gas bill showing 50 therms equals about 1,465 kWh of energy in the gas. Some utilities bill in hundred cubic feet (CCF), which is close to one therm but varies with gas heat content.
How many kW is a 12,000 BTU air conditioner?
A 12,000 BTU per hour rating equals 3.52 kW of cooling, also called 1 ton. That is heat moved, not electricity used. Because air conditioners and heat pumps move several units of heat per unit of electricity, a 1-ton unit typically draws around 1 kW or less of electrical power.
Is BTU energy or power?
BTU is a unit of energy, like kWh, and 1 kWh equals 3,412.14 BTU. BTU per hour (BTU/h, often written just BTU on equipment labels) is a unit of power, like kW. Furnaces, boilers and air conditioners are rated in BTU/h.
How do I compare gas and electric heating costs?
Convert both to the same unit. A therm is 29.31 kWh of heat, but a gas furnace delivers only part of that as useful heat depending on its efficiency, while a heat pump delivers more heat than the electricity it uses. Divide the fuel price by the useful kWh delivered to compare.
How many kWh is 1 million BTU?
One million BTU (1 MMBtu) equals about 293.07 kWh. Natural gas wholesale prices are often quoted per MMBtu, so this conversion helps compare them with electricity prices per kWh.
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Last updated October 25, 2026. Part of our renewable energy toolkit. Found an error? Tell us.