How many joules are in a kilowatt-hour?

One kilowatt-hour (kWh) equals exactly 3,600,000 joules (3.6 × 10⁶ J). This follows from the definition: 1 W = 1 J/s, and 1 hour = 3,600 s, so 1 kWh = 1,000 W × 3,600 s = 3,600,000 J.

How do I convert joules to kilowatt-hours?

Divide the number of joules by 3,600,000. For example, 7,200,000 J ÷ 3,600,000 = 2 kWh.

How do I convert kilowatt-hours to joules?

Multiply the number of kilowatt-hours by 3,600,000. For example, 0.5 kWh × 3,600,000 = 1,800,000 J.

What is a watt-hour (Wh) and how does it relate to joules?

A watt-hour equals 3,600 joules (1 W × 3,600 s). It is 1/1,000 of a kilowatt-hour. Battery capacities are often quoted in Wh, while electricity billing uses kWh.

Why are joules so small compared to kWh?

A joule is a very small amount of energy — roughly the energy needed to lift a 100 g object by 1 metre. A kilowatt-hour represents the energy drawn by a 1,000-watt appliance running for a full hour, making it 3.6 million times larger than a joule.

Is this conversion exact?

Yes. By SI definition, 1 kWh = 3.6 × 10⁶ J exactly. No approximation is involved.

Joules to Kilowatt Hours Converter

Name: Joules to Kilowatt Hours Converter
Availability: InStock
Author: Nham Vu

Convert joules to kilowatt-hours (or kWh to J) instantly — 1 kWh = 3,600,000 J exactly.

Energy Converter

Value in joules (J)

Kilowatt-hours (kWh)

—

Watt-hours (Wh) —

kWh = J ÷ 3,600,000

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Quick Reference Table

Joules (J)	kWh	Wh

kWh	Joules (J)	Wh

1 kWh = 3,600,000 J (exact) • 1 Wh = 3,600 J • 1 J = 2.77778×10^-7 kWh

Summary

Convert joules to kilowatt-hours (or kWh to J) instantly — 1 kWh = 3,600,000 J exactly.

How it works

Select a conversion direction: J to kWh, or kWh to J.
Enter your energy value in the input field.
The result appears instantly in kWh and Wh (or J), with the formula shown.
Click Swap to reverse direction without clearing your value.
Use the reference table to look up common conversions at a glance.

Use cases

Convert physics or engineering energy values from joules to the kWh used on electricity bills.
Estimate battery capacity: convert joule ratings (e.g. from datasheets) into kWh.
Cross-check solar panel output figures given in joules against kWh meter readings.
Convert calorimetry or thermodynamics results into electrical energy equivalents.
Understand how many joules are stored in a 1 kWh home battery pack.
Verify unit conversions in science homework or exam problems.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu