BTU to kWh Calculator: Convert Heat Units

This BTU to kWh calculator converts energy measured in British thermal units (BTU) into kilowatt-hours (kWh) and vice versa. You enter a number in either unit and get the equivalent in the other, using the standard conversion factor 1 kWh = 3,412 BTU (International Table). The calculator also shows the result in watt-hours and megajoules for context.

Formula

The conversion is a fixed ratio between two units of energy. The formula is:

kWh = BTU ÷ 3,412

And the reverse:

BTU = kWh × 3,412

Where:

• BTU – British thermal unit, the energy needed to raise 1 pound of water by 1°F (about 1,055 joules).
• kWh – kilowatt-hour, the energy used by a 1,000-watt device running for 1 hour (3.6 million joules).

The factor 3,412 comes from the definition: 1 kWh = 3,600,000 J and 1 BTU = 1,055.05585 J, so 3,600,000 ÷ 1,055.05585 ≈ 3,412.14. Most practical conversions round to 3,412.

Worked Example

Using the default input of 10,000 BTU:

1. Start with the formula: kWh = BTU ÷ 3,412.
2. Plug in the value: kWh = 10,000 ÷ 3,412.
3. Perform the division: 10,000 ÷ 3,412 ≈ 2.9308.
4. Round to 3 decimal places: 2.931 kWh.

The calculator also shows that 10,000 BTU equals 10,000 × 1,055.05585 ≈ 10,550,558 J = 2.931 kWh, and in watt-hours that is 2,931 Wh. In megajoules, 10,000 BTU ≈ 10.551 MJ.

Why Convert BTU to kWh?

BTU is common in the United States for heating and cooling equipment – furnaces, air conditioners, water heaters, and gas stoves. Electricity bills, however, are measured in kWh. If you want to compare the cost of running a gas heater versus an electric one, or estimate how much electricity a heat pump uses, you need to convert its BTU rating into kWh.

For example, a 12,000 BTU window air conditioner (about 1 ton) uses roughly 12,000 ÷ 3,412 ≈ 3.52 kWh if it ran for one hour at full power. In reality, it cycles on and off, so actual daily usage is lower, but the conversion gives you a ceiling.

How to Read the Result

The first output line is the headline answer: kilowatt-hours. A result of 2.931 kWh means that if you ran a device consuming 10,000 BTU per hour for one hour, it would use 2.931 kWh of electricity. For a monthly estimate, multiply by hours of operation per day and by 30.

Keep in mind that BTU ratings on appliances are often per hour (BTU/h), not total energy. The calculator assumes you are entering total BTU for a given period. If your appliance label says “12,000 BTU/h,� that is the power rate, not energy. To get total BTU for a day, multiply by hours run.

Common Mistakes and Pitfalls

• Confusing BTU with BTU/h – A furnace rated 60,000 BTU/h is not 60,000 BTU total; it’s that much per hour. Always check the time unit.
• Using the wrong conversion factor – Some sources use 3,412.14, others 3,412. The difference is less than 0.005%, so it rarely matters. For large numbers, use 3,412.14 for precision.
• Mixing up kWh and kW – kW is power (rate), kWh is energy (amount). A 1 kW heater running 1 hour uses 1 kWh. The calculator converts energy, not power.
• Forgetting that BTU is a unit of heat, not electricity – When comparing gas vs. electric, you also need efficiency. A gas furnace at 80% efficiency converts only 80% of the BTU in the fuel into heat.

Real-World Examples

Here are a few typical conversions to give you a feel:

• 5,000 BTU (small window AC) → 5,000 ÷ 3,412 ≈ 1.465 kWh per hour of full operation.
• 30,000 BTU (gas water heater) → 30,000 ÷ 3,412 ≈ 8.792 kWh per hour of burn.
• 100,000 BTU (whole-house furnace) → 100,000 ÷ 3,412 ≈ 29.31 kWh per hour of run time.

To convert the other way, multiply kWh by 3,412. For instance, a 1.5 kWh electric heater produces 1.5 × 3,412 ≈ 5,118 BTU of heat per hour.

Efficiency and Cost Considerations

The conversion factor only handles energy units. Actual cost comparison requires efficiency ratings:

• Electric resistance heat – nearly 100% efficient (all electricity becomes heat).
• Gas furnace – 80% to 98% AFUE (Annual Fuel Utilization Efficiency).
• Heat pump – can deliver 2 to 4 BTU of heat per watt-hour (i.e., a COP of 2–4), so it uses far less kWh per BTU than resistance heating.

For a rough cost estimate, multiply the kWh by your electricity rate (e.g., $0.15/kWh). For gas, multiply therms by the gas rate. One therm equals 100,000 BTU, so a 100,000 BTU furnace uses exactly 1 therm per hour of full operation.

Limitations of the Conversion

This calculator is purely a unit converter. It does not account for:

• Efficiency losses in appliances (combustion, heat loss, cycling).
• Time – you must decide the period yourself (hour, day, month).
• Different BTU definitions (ISO, IT, thermochemical) – differences are under 0.1%.
• Altitude or temperature effects on gas heating values – negligible for most home use.

For appliance sizing or energy audits, use the manufacturer’s rated BTU/h and actual run time, not just the label.

Frequently Asked Questions

How many BTU are in 1 kWh?

Exactly 3,412 BTU (International Table). So 1 kWh = 3,412 BTU. If you see a heater rated 5,000 BTU, that’s about 1.465 kWh of heat energy.

Is BTU the same as BTU/h?

No. BTU is a unit of energy (like joules). BTU/h is a unit of power (like watts). A device rated 12,000 BTU/h consumes 12,000 BTU of energy every hour it runs. To get total BTU, multiply the rate by hours.

How do I convert my furnace’s BTU rating to kWh?

Divide the BTU rating by 3,412 to get kWh per hour of full operation. For example, a 60,000 BTU furnace uses 60,000 ÷ 3,412 ≈ 17.58 kWh per hour of burn. Multiply by actual run hours to get daily or monthly energy.

Why do air conditioners use BTU instead of watts?

BTU is a traditional unit for heat energy in the US, and AC capacity is measured by how much heat it can remove per hour. Watts are more common for electrical power. The conversion helps compare cooling capacity with electrical consumption.

What is a therm and how does it relate to BTU?

A therm is a unit of heat equal to 100,000 BTU. Natural gas bills in the US often use therms. To convert therms to kWh, multiply by 100,000 and divide by 3,412: 1 therm ≈ 29.3 kWh.

Can I use this calculator for both heating and cooling?

Yes. BTU is a measure of heat energy regardless of direction. The conversion to kWh is the same for a furnace, a heat pump, or an air conditioner. Just remember that cooling efficiency (SEER) and heating efficiency (AFUE) are different.

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in btu | BTU | BTU | 10000 | 0
in kwh | kWh | kWh | 0 | 0
out kwh | Kilowatt-hours | kWh | btu / 3412 | 3
out btu | BTU | BTU | kwh * 3412 | 0
out wh | Watt-hours | Wh | btu / 3.412 | 1
out mj | Megajoules | MJ | btu / 947.8 | 3