Basics
Watts to kWh Calculator and Formula
kWh is the unit most electricity bills use to measure energy consumption.
Formula
kWh = Watts / 1000 x Hours UsedA 1,500 watt appliance running for 4 hours uses 6 kWh.
What watts and kWh mean
Watts measure how much power an appliance draws at a moment in time. Kilowatt-hours measure how much energy that appliance uses over time. Your utility bill usually charges by kilowatt-hour, so converting watts to kWh is the bridge between an appliance label and a cost estimate.
A high-wattage appliance does not always cost the most. A microwave may use more than 1,000 watts, but only for a few minutes. A refrigerator may use fewer watts while running, but it cycles on and off every day. The kWh formula lets you compare both cases using the same unit.
Watts to kWh examples
| Appliance example | Watts | Hours used | Energy used |
|---|---|---|---|
| Space heater | 1,500W | 4 hours | 6 kWh |
| Box fan | 60W | 8 hours | 0.48 kWh |
| Electric dryer | 3,000W | 1 hour | 3 kWh |
| Laptop | 65W | 8 hours | 0.52 kWh |
How to use kWh for cost
After you know kWh, multiply it by your electricity rate. If a heater uses 6 kWh and your rate is $0.17 per kWh, the estimated cost is $1.02. If your rate is $0.25 per kWh, the same use costs $1.50.
Cost = kWh x Electricity RateThis is why WattCostGuide calculators ask for both usage time and electricity rate. The same appliance can have very different monthly costs in different homes or on different utility plans.
Watts to kWh FAQ
Is 1,000 watts the same as 1 kWh?
Not exactly. One thousand watts is 1 kilowatt of power. If a 1,000 watt appliance runs for 1 hour, it uses 1 kilowatt-hour, or 1 kWh, of energy.
Should I use 24 hours for appliances that stay plugged in?
Only if the appliance actually draws that wattage all day. Refrigerators, freezers, aquarium heaters, and similar devices cycle on and off, so active runtime is usually more useful than plugged-in time.
Where do I find appliance watts?
Start with the product label, owner manual, charger label, or manufacturer specifications. If you need a better real-world number, a plug-in energy monitor can measure actual watts and kWh.
Try the formula with real appliances
Open a calculator and adjust watts, hours, and electricity rate for a practical estimate.
Next guides to read
Continue with the cost formula, appliance wattage, and electricity rate basics.