Kilojoules to kilowatt-hours (kJ to kWh) converter

What is a kilojoules to kilowatt-hours converter?

A kilojoules to kilowatt-hours converter is an online tool that turns an amount of energy expressed in kilojoules (kJ) into its equivalent in kilowatt-hours (kWh), and the other way around. Both units measure the same physical quantity — energy — but they come from different worlds. The joule (and its multiple, the kilojoule) is the SI unit favoured in physics, chemistry, and nutrition labelling, while the kilowatt-hour is the practical unit you see on electricity meters and utility bills. This converter lets you move between the scientific value and the billing value without doing the arithmetic by hand.

How it works

The conversion rests on the definition of the kilowatt-hour: it is the energy delivered by a power of one kilowatt sustained for one full hour. Since one kilowatt equals 1,000 joules per second, and one hour equals 3,600 seconds, one kilowatt-hour equals 1,000 × 3,600 = 3,600,000 joules, which is 3,600 kilojoules.

In other words, every kilowatt-hour is exactly 3,600 kilojoules. To go from kilojoules to kilowatt-hours you divide by 3,600; to go from kilowatt-hours to kilojoules you multiply by 3,600. The relationship is exact — there is no rounding hidden in the factor — so the only approximation you ever introduce is when you decide how many decimal places to keep.

Formula

$\text{kWh} = \frac{\text{kJ}}{3600}$

And to convert in the opposite direction:

$\text{kJ} = \text{kWh} \times 3600$

Kilojoules to kilowatt-hours conversion table

The table below shows common kilojoule values together with their kilowatt-hour equivalents.

Examples

Example 1: One kilowatt-hour in kilojoules

A kilowatt-hour is the headline unit on your electricity bill. Converting 3,600 kJ shows exactly how much energy that represents:

$\frac{3600}{3600} = 1 \text{ kWh}$

So 3,600 kilojoules is precisely one kilowatt-hour.

Example 2: Five kilowatt-hours to kilojoules

Suppose an appliance uses 5 kWh over a day and you want the figure in kilojoules:

$5 \times 3600 = 18{,}000 \text{ kJ}$

Five kilowatt-hours equals 18,000 kilojoules.

Example 3: Converting 7,200 kilojoules

A battery is rated at 7,200 kJ of stored energy. In billing units that is:

$\frac{7200}{3600} = 2 \text{ kWh}$

Example 4: A larger value

Converting 36,000 kJ gives a round result that is handy for a quick mental check:

$\frac{36000}{3600} = 10 \text{ kWh}$

Notes

• The factor 3,600 kJ per kWh is exact by definition, so conversions are reversible with no loss of accuracy beyond the decimals you choose to keep.
• Because one kilojoule is a small slice of a kilowatt-hour (about 0.000278 kWh), kilojoule values that look large often translate into modest kilowatt-hour figures.
• Do not confuse energy (kJ, kWh) with power (kW). Power is the rate of using energy; a kilowatt-hour is the energy used by one kilowatt running for an hour.
• The same converter also handles joules, megajoules, and calories, so you can chain conversions without leaving the page.

Frequently asked questions

How many kilojoules are in one kilowatt-hour?

There are exactly 3,600 kilojoules in one kilowatt-hour, because 1 kWh equals 3,600,000 joules and a kilojoule is 1,000 joules.

How do I convert kilojoules to kilowatt-hours?

Divide the number of kilojoules by 3,600. For example, 7,200 kJ ÷ 3,600 = 2 kWh.

How do I convert kilowatt-hours back to kilojoules?

Multiply the number of kilowatt-hours by 3,600. For example, 5 kWh × 3,600 = 18,000 kJ.

How many kilowatt-hours is 1,000 kJ?

One thousand kilojoules is about 0.2778 kWh (1,000 ÷ 3,600). That is roughly a quarter of a kilowatt-hour.

Are kilojoules and kilowatt-hours the same kind of unit?

Yes. Both measure energy, so they can be converted into each other directly. They simply belong to different conventions — kilojoules in science and nutrition, kilowatt-hours in electricity metering.

Why is the conversion factor exactly 3,600?

Because a kilowatt-hour is one kilowatt applied for one hour, and an hour contains 3,600 seconds. One kilowatt is 1 kilojoule per second, so 3,600 seconds gives 3,600 kilojoules.