Kwh From Watts
Calculator
Results
- Energy (kWh)
- 3
- Energy (MJ)
- 10.8
- Energy cost
- 0.51
Energy results
| Energy (kWh) | 3 |
| Energy (MJ) | 10.8 |
| Energy cost | 0.51 |
formula-map diagram
- Energy (kWh)
- 3
- Energy (MJ)
- 10.8
- Energy cost
- 0.51
Energy relationship
Formula
E(kWh) = P(W) × t(h) ÷ 1000= 3
Note
This is a simplified model: it applies the standard equation to the numbers you entered and ignores real-world losses, weather variation, tariff structures and equipment tolerances. Wind power assumes air density 1.225 kg/m³ at ISA sea level and the power coefficient you enter (Betz limit 0.593). Verify with measured data or a professional energy audit before making purchasing decisions.
More in Energy and environment
See all →Frequently asked questions
What's the difference between watts and kilowatt-hours?+
Watts measure the rate of power draw at any instant, like speed; kilowatt-hours measure total energy consumed over time, like distance traveled. A device can draw a high wattage but still use little energy if it only runs briefly.
What's the exact formula used here?+
kWh = (watts × hours) ÷ 1000. The division by 1000 converts watts into kilowatts before multiplying by the run time, since utilities bill in kilowatt-hours rather than watt-hours.
Why does the same appliance show different kWh on different days?+
Because kWh depends on how long the device actually runs, not just its rated wattage. A thermostat-controlled appliance like a fridge or heater cycles on and off, so its effective daily hours of full-power draw vary with conditions.
Can I use this for devices with variable power draw?+
You'll get a rough estimate at best, since variable-speed motors and electronics draw different wattages depending on load. For those, an average wattage over a measured period, ideally from a plug-in energy meter, gives a far more reliable result than the nameplate rating.
How do I convert the result into a cost?+
Multiply the kWh figure by your utility's price per kilowatt-hour, which you can find on a recent bill. This calculator only handles the watts-to-energy conversion step; pairing it with your rate gives the dollar cost.