Gas appliances are rated in MJ/h — what does that mean in kW?

Divide by 3.6: a 36 MJ/h gas burner draws 10 kW of thermal power.

Why does my gas bill show MJ?

Australian and several European gas utilities bill in megajoules, while electricity is billed in kWh. Converting both to the same unit is the only way to compare heating costs fairly.

How many MJ in a typical household day?

An average European home uses about 10.5 kWh of electricity per day, which is roughly 38 MJ.

MJ to kWh Converter | Megajoules to Kilowatt-hours

Conversion Formula

kWh = MJ ÷ 3.6

Divide megajoules by 3.6 to get kilowatt-hours. The factor is exact — no rounding error is introduced in either direction.

Complete Guide to Megajoules to Kilowatt-hours Conversion

What is a Megajoules?

A megajoule (MJ) is one million joules, the SI unit of energy. It is used in fuel energy content labels, gas tariffs in Australia and parts of Europe, appliance efficiency standards and all scientific literature.

What is a Kilowatt-hours?

A kilowatt-hour (kWh) is the amount of energy delivered by one kilowatt of power sustained for one hour. It is the billing unit for electricity almost everywhere in the world and the standard way to express battery capacity, solar production and household consumption.

How the Conversion Works

The conversion rests on the definition of the watt as one joule per second. One kilowatt is 1,000 joules per second; run it for one hour (3,600 seconds) and you have delivered 3,600,000 joules, which is 3.6 MJ. Because both units are SI-derived, the factor is exact.

Why This Conversion Matters

Households that heat with gas and drive on electricity are billed in two different energy units. Converting both to a common unit is the only way to answer the practical question: is it cheaper to heat this room with gas or with a heat pump? The same conversion underpins comparisons between fuel energy content and battery capacity.

Scientific Context

The joule is defined as the work done when a force of one newton moves an object one metre. The kilowatt-hour is a practical, non-SI unit retained for commercial metering. IEC and ISO standards express energy in joules; utility regulation almost universally uses kWh.

Step-by-Step Conversion Guide

Follow these steps to convert megajoules to kilowatt-hours manually:

Start with your value in megajoules

Example: You want to convert 10 MJ

Apply the conversion formula

Use the formula: kWh = MJ ÷ 3.6

Calculate the result

10 MJ = 2.7778 kWh

✓

Verify your answer

Use our calculator above to double-check your manual calculation.

Quick Mental Math Tip

Divide megajoules by 3.6 to get kilowatt-hours. The factor is exact — no rounding error is introduced in either direction.

Common Conversions

Megajoules to Kilowatt-hours conversion table
Megajoules (MJ)	Kilowatt-hours (kWh)	Kilowatt-hours → Megajoules
1	0.2778	1 kWh = 3.6 MJ
3.6	1	3.6 kWh = 12.96 MJ
10	2.7778	10 kWh = 36 MJ
36	10	36 kWh = 129.6 MJ
50	13.8889	50 kWh = 180 MJ
100	27.7778	100 kWh = 360 MJ
180	50	180 kWh = 648 MJ
360	100	360 kWh = 1296 MJ
1000	277.7778	1000 kWh = 3600 MJ

When You'll Need This Conversion

Comparing gas and electricity bills

Gas tariffs in MJ and electricity tariffs in kWh cannot be compared until both are expressed in the same unit.

Engineering datasheets

Industrial equipment and efficiency standards state energy consumption in MJ, while the meter on the wall reads kWh.

Physics and energy coursework

Converting between the practical unit (kWh) and the SI unit (J) is a standard exercise in energy calculations.

Heating system sizing

Boiler and heat pump outputs are quoted in kW or MJ/h depending on the market — converting keeps sizing calculations consistent.

Pro Tips for Accurate Conversions

Remember 3.6, not 3.16

3.6 comes from 3,600 seconds in an hour. If you ever see 3.16 you are looking at a different factor entirely.

MJ/h is just kW × 3.6

A 24 MJ/h gas heater is a 6.7 kW heater. This one trick makes every gas appliance comparable to an electric one.

Divide gas MJ by 3.6 before comparing prices

Convert the gas rate to a per-kWh price, then compare against the electricity rate divided by heat pump COP (typically 3).

Common Mistakes to Avoid

Confusing kW with kWh

A kilowatt is a rate of energy flow; a kilowatt-hour is a quantity of energy. A 2 kW heater running for 30 minutes uses 1 kWh.

Power (kW) × time (h) = energy (kWh). Only kWh converts to MJ.

Comparing gas MJ directly against electric kWh prices

A megajoule is far smaller than a kilowatt-hour, so gas always looks artificially cheap per unit.

Convert MJ to kWh first (÷ 3.6), then compare unit prices.

Ignoring appliance efficiency

A gas boiler at 90% efficiency and a heat pump at 300% efficiency deliver very different heat from the same input energy.

Convert to delivered heat: input energy × efficiency, then compare.

History & Background

The joule was named after James Prescott Joule, whose 1840s experiments established the mechanical equivalent of heat. The kilowatt-hour emerged with commercial electricity metering in the 1880s as a unit customers could understand.

Key Milestones

1843

Joule demonstrates the mechanical equivalent of heat, linking work and energy.

1882

Edison's Pearl Street Station begins metered electricity supply, popularising the kilowatt-hour.

1948

The 9th CGPM adopts the joule as the SI unit of energy, heat and work.

2019

SI base units are redefined from physical constants, fixing the joule via the Planck constant.

Global Usage Today

kWh dominates electricity billing worldwide. MJ is standard in Australian gas billing, EU appliance energy labels, fuel energy content declarations and all scientific publishing.