What Is a kWh?
A kWh (kilowatt-hour) measures electricity consumption over time. One kWh equals 1,000 watts used for one hour. It's what electric companies bill you for—the average US price is about $0.16 per kWh.
Key Takeaways
- Watts measure instantaneous power draw, while kilowatt-hours measure total energy consumed over time.
- Some utilities have tiered rates—first 500 kWh might cost less than the next 500.
- Time-of-use rates vary by time of day—peak hours cost more.
Explanation
Watts measure instantaneous power draw, while kilowatt-hours measure total energy consumed over time. A 100-watt light bulb running for 10 hours uses 1 kWh (100W × 10h = 1,000Wh = 1kWh).
Your electric bill shows total kWh used during the billing period. To calculate cost: kWh × rate per kWh = cost. If you used 1,000 kWh at $0.16/kWh, your bill would be $160.
Understanding kWh helps you estimate appliance costs. A 1,500W space heater running 8 hours uses 12 kWh, costing about $1.92 per day at average rates.
Common household appliances vary enormously in kWh consumption. A refrigerator uses about 1-2 kWh per day (400-800 kWh per year), a central air conditioner uses 3-5 kWh per hour during operation, and a clothes dryer uses roughly 2-5 kWh per load. LED bulbs use only 0.01 kWh per hour (10 watts), while old incandescent bulbs used 0.06 kWh per hour (60 watts) for the same brightness. Replacing ten 60W incandescent bulbs with 10W LEDs and running them 5 hours daily saves about 912 kWh per year, or roughly $146 at the national average rate.
The average US household consumes about 10,500 kWh per year, but this varies dramatically by region. Homes in Louisiana and Texas average over 14,000 kWh annually due to air conditioning demand, while households in Hawaii and California average under 6,500 kWh because of milder climates and higher electricity prices that incentivize conservation. Electric vehicle owners can expect to add 3,000-4,500 kWh per year for a car driven 12,000 miles, since most EVs consume 25-35 kWh per 100 miles. Solar panels in a sunny climate produce about 1,500 kWh per installed kilowatt per year, so a 7 kW home system would generate roughly 10,500 kWh, enough to offset the average household's entire consumption.
Things to Know
- Some utilities have tiered rates—first 500 kWh might cost less than the next 500.
- Time-of-use rates vary by time of day—peak hours cost more.
- 1 kWh = 3,412 BTU, useful when comparing to gas appliance costs.
- Standby power (phantom load) from electronics left plugged in but turned off can add 200-400 kWh per year to a household's consumption, costing $30-65 annually for devices that appear to be off.