A kilowatt-hour (kWh) is the standard unit used to measure electricity consumption — and it appears on every electricity bill, solar system report, and EV range specification in the world. Understanding it takes about two minutes and will make every energy decision you ever make much clearer.
One kWh = using 1,000 watts of power for 1 hour.
That's it. Everything else is just applying that definition.
The easiest way to understand kWh is through everyday appliances:
These three terms confuse almost everyone at first:
The analogy: watts/kilowatts are like speed (km/h), and kilowatt-hours are like distance (km). A car going 60km/h for 2 hours travels 120km. An appliance using 0.5kW for 2 hours uses 1 kWh.
Your electricity bill charges you per kWh consumed. Rates vary significantly by country:
To calculate your appliance cost: multiply its wattage × hours used ÷ 1000 × your electricity rate. A 2,400W electric shower used for 8 minutes per day: 2400 × (8/60) ÷ 1000 × $0.30 = $0.096/day = $35/year.
Solar panels are rated in kilowatts (kW) — their peak power output in ideal conditions. A 6.6kW solar system in a sunny location might generate 25–30 kWh on a good day. That's 6.6kW × roughly 4–5 peak sun hours of equivalent production.
Battery storage capacity is also measured in kWh. A Tesla Powerwall holds 13.5 kWh — enough to run a typical home for 12–24 hours depending on consumption.
EV battery capacity is measured in kWh. The larger the battery, the more range. Common examples:
EV efficiency is measured in kWh/100km. A typical EV uses 15–20 kWh/100km. At $0.30/kWh home charging, that's $4.50–$6.00 per 100km — vs $12–$18 per 100km for a petrol car.
To find how much any appliance costs to run:
Daily cost = Watts ÷ 1000 × Hours per day × Cost per kWh
Examples at $0.30/kWh: