kWh, watts & cost calculator
Watts × hours → kWh → cost
Amps × volts → watts
BTU → watts
kWh → cost
Frequently asked questions
How do I convert watts to kWh?
kWh = watts × hours ÷ 1,000. A 1,500 W heater running 4 hours uses 1,500 × 4 ÷ 1,000 = 6 kWh.
How do I convert amps to watts?
Watts = amps × volts. A device drawing 10 A on a 120 V outlet uses about 1,200 W. On a 240 V circuit, 10 A is 2,400 W. Motors draw a little less real power than this (power factor 0.8–0.95).
How many watts is a BTU?
1 watt = 3.412 BTU per hour, so a 5,000 BTU/h heater uses about 1,465 W. Air conditioners move more heat than they use. An AC's watts ≈ BTU/h ÷ EER (for example, 8,000 BTU ÷ 12 EER ≈ 667 W).
How much does 1 kWh cost?
The U.S. average residential price is shown in the rate bar above. Enter your ZIP for your utility's price, then multiply by kWh to get cost.