Energy Unit Converter
Convert between the units that show up on appliance labels and electricity bills — watts, kilowatts, kilowatt-hours, volts and amps.
Energy (kWh) = Power (W) × Hours ÷ 1000. This is the core formula behind every electricity bill.
Per day
0.5 kWh
Per week
3.5 kWh
Per month
15.22 kWh
Per year
182.5 kWh
Understanding energy units
Watts vs. kilowatt-hours
A watt (W) measures power — how fast energy is used at any moment. A kilowatt-hour (kWh) measures energy — power sustained over time. Running a 1,000 W device for one hour uses 1 kWh.
Why your bill uses kWh
Utilities charge for total energy consumed, not instantaneous power. That is why the bill is in kilowatt-hours, while your appliance nameplate lists watts.
Ohm's law basics
Power equals voltage times current (W = V × A). If you know two of the three, you can find the third — useful for sizing circuits or checking a nameplate rating.
Everyday reference points
An LED bulb is about 9 W, a laptop 50 W, a microwave 1,200 W, and an electric kettle 2,000 W. Multiply by hours of use to see how quickly each adds up.
Related calculators
Electricity Bill Calculator
Estimate your electricity bill from usage or appliance power — flat or tiered rates.
Appliance Cost Calculator
See what any appliance costs to run per day, month, and year.
Bill Splitter
Split an electricity bill fairly between roommates or tenants.
Reverse Bill Calculator
Work backwards from a bill amount to estimate how many kWh you used.