Watt-hour (Wh)

Definition

One watt sustained for one hour, exactly 3600 joules — one thousandth of a kilowatt-hour.

History

The watt-hour is the energy of one watt delivered for one hour, exactly 3600 joules. It is one thousandth of the kilowatt-hour used on electricity bills.

Where it is used

Watt-hours rate battery capacity — phone, laptop and power-bank batteries are labelled in Wh or mWh.

Typical uses include battery capacity, small appliances.

Conversion pages

These pages convert watt-hour to or from another unit in energy.

No conversion pages use this unit yet.

Other Energy units

• Kilocalorie (kcal)
• Kilojoule (kJ)
• Calorie (cal)
• Joule (J)
• Kilowatt-hour (kWh)
• British thermal unit (BTU)

Sources

• NIST SP 811 NIST SP 811, Appendix B; ISO 80000-5 (energy) · Dataset reviewed Nov 11, 2026