What is a kilowatt-hour (kWh)?

A kilowatt-hour is the amount of energy consumed by a 1,000-watt appliance running for one hour. It's the standard billing unit on electric bills worldwide. For example, a 100W light bulb running for 10 hours uses 1 kWh.

What is the difference between watts and kilowatt-hours?

Watts (W) measure power — the rate of energy use at any instant. Kilowatt-hours (kWh) measure energy — the total amount consumed over time. Think of watts as speed and kWh as distance travelled.

How do I calculate my appliance electricity cost?

Multiply the appliance wattage by hours of daily use, divide by 1,000 to get kWh, then multiply by your electricity rate. Formula: (Watts x Hours) / 1000 x Rate = Daily cost.

Electricity Units Explained: kWh, Watts, Amps, and Volts Demystified

The Four Key Electricity Units

Understanding these four units helps you read your electric bill, compare appliances, and save money.

Volts (V) — Electrical Pressure

Voltage is the "pressure" that pushes electricity through wires. In most countries, household outlets provide either 110-120V (North America, Japan) or 220-240V (Europe, Asia, Australia).

Amps (A) — Electrical Flow

Amperage measures how much electricity is flowing. Higher amps mean more current. A typical household circuit is rated for 15-20 amps.

Watts (W) — Power

Watts measure the rate of energy consumption. The formula is simple:
Watts = Volts x Amps

A 120V outlet delivering 10 amps provides 1,200 watts of power.

Kilowatt-hours (kWh) — Energy

This is what you pay for. One kWh = 1,000 watts used for one hour.
kWh = (Watts x Hours) / 1,000

Common Appliance Power Usage

Appliance	Typical Watts	Daily kWh (est.)
LED light bulb	10W	0.1
Laptop	50W	0.4
Desktop computer	200W	1.6
Refrigerator	150W	1.5
Washing machine	500W	0.5
Air conditioner	1,500W	6.0
Electric oven	2,500W	2.5
EV charger (Level 2)	7,700W	30.0
Hair dryer	1,800W	0.3

How to Read Your Electric Bill

Your electric bill charges per kWh. The average electricity rate varies globally:

USA: ~$0.16/kWh

UK: ~$0.34/kWh

Germany: ~$0.40/kWh

Australia: ~$0.30/kWh

To estimate monthly cost for any appliance: (Watts x Hours/day x 30) / 1,000 x Rate

For example, running a 1,500W space heater 8 hours/day: (1500 x 8 x 30) / 1000 x $0.16 = $57.60/month

Energy Saving Tips

Switch to LED bulbs — use 75% less energy than incandescent

Unplug vampire loads — chargers and standby devices waste 5-10% of household energy

Use a smart thermostat — can reduce heating/cooling costs by 10-15%

Run appliances off-peak — many utilities offer cheaper night rates

Convert between energy units with our Energy Converter — instantly convert kWh, joules, calories, BTU, and more.