kWh to MJ Calculator
Convert energy between kilowatt-hours, megajoules, BTU, therms and kilocalories — useful when bills, gas and solar figures are quoted in different units.
1 kWh is the energy of a 1,000 W appliance running for one hour — the unit your electricity bill and solar production are measured in.
How this conversion works
1 kWh = 3.6 MJ = 3,412 BTU, 1 therm = 105.5 MJ, 1 kcal = 4,184 J, 1 Wh = 3,600 J.So 1 kWh = 3.6 MJ, and 1 MJ ≈ 0.278 kWh.
Why energy units get mixed up
Electricity bills and solar production use kilowatt-hours; scientists and gas suppliers use megajoules, therms or BTU; food and heating sometimes use kilocalories. They all measure the same thing — energy — so any figure converts cleanly through joules. This is handy when comparing a solar system’s kWh output against a gas bill in therms or MJ.
Quick anchors
1 kWh = 3.6 MJ = 3,412 BTU ≈ 860 kcal. A typical home using 30 kWh a day consumes about 108 MJ. One therm of gas (about 105.5 MJ) equals roughly 29.3 kWh of energy content.
Everyday energy amounts, converted
| Energy | kWh | MJ | BTU |
|---|---|---|---|
| Boiling 1 L of water | 0.11 | 0.40 | 380 |
| One dishwasher cycle | 1.2 | 4.3 | 4,100 |
| Daily output of 1 kW of solar (4.5 sun-hrs) | 4.5 | 16.2 | 15,350 |
| Typical home, per day | 15–30 | 54–108 | 51k–102k |
| 1 therm of gas | 29.3 | 105.5 | 100,000 |
| 1 litre of diesel (energy content) | 10.7 | 38.6 | 36,500 |
The diesel row explains generator economics at a glance: a litre holds ~10.7 kWh of heat, but a small genset converts only ~3 kWh of it to electricity — the rest is lost as heat and noise.
Frequently asked questions
One kilowatt-hour equals exactly 3.6 megajoules, because 1 kWh is 1,000 watts for 3,600 seconds.
Divide megajoules by 3.6. For example, 18 MJ / 3.6 = 5 kWh.
About 3,412 BTU per kilowatt-hour.
One therm is about 29.3 kWh of energy content, or roughly 105.5 MJ. Gas bills often use therms or MJ while solar is measured in kWh.
Sources & standards
This is a pure energy-unit conversion tool, so its constants come from SI definitions and official government energy-content data rather than solar policy.
- NIST Special Publication 811 — Guide for the Use of the International System of Units (SI) — National Institute of Standards and Technology
Source for the exact kWh-to-joule and kWh-to-BTU conversion factors used throughout the calculator. - The International System of Units (SI Brochure) — Bureau International des Poids et Mesures
Defines the joule and megajoule as the underlying SI energy unit that kWh, BTU and therms all convert through. - British thermal units (Btu) — Energy explained — U.S. Energy Information Administration
Reference for BTU and therm energy-content figures used to compare gas bills against solar kWh output. - How to convert natural gas prices between cubic feet, therms and Btu — U.S. Energy Information Administration
Basis for the therm-to-kWh and therm-to-MJ figures quoted in the conversion table.