Electricity usage calculator
Kilowatt-hours an appliance uses and what that costs.
Fill in the fields and the result will appear here automatically.
Converts an appliance rating into kilowatts once, then multiplies by the hours it runs and the days you are counting. Watts and kilowatt-hours are easy to confuse — one is power, the other is energy accumulated over time — so the conversion happens in one visible step. Add your tariff and the cost follows.
How it works
Formula and logic
Divide watts P by 1000; entered kilowatts need no conversion. Daily energy=P_kW×h and period energy=P_kW×h×d, with 0≤h≤24 and positive whole days d. The 30-day row always uses 30, independently of the chosen period. Costs appear only for a positive tariff; blank or 0 omits them. The model holds the entered average power for h hours.
Example
A 2000 W heater for 3 hours a day over 30 days uses 2 × 3 × 30 = 180 kWh. Zero hours gives zero energy and zero cost; a blank tariff omits costs, while fractional days are rejected.
Fields and units
- Appliance power — in the selected power unit
- Power unit — list option
- Hours per day — h/day
- Number of days — days
- Tariff per kWh — $
How to use
- — Use the selected operating power from the label or measure average power over your operating hours.
- — Enter how many hours a day it runs and over how many days.
- — Add your tariff for the cost.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- Virginia Cooperative Extension, 2020: power × hours and tariff; operating settings affect actual use
- Limitation
- The 30-day row always uses 30, independently of the chosen period. The model holds the entered average power for h hours.
FAQ
Where do I find my tariff?
On your electricity bill, as a price per kilowatt-hour. Multi-rate meters are not modelled, so work out each rate band separately.
Is the label power what it actually draws?
Not necessarily. A label may state rated power or several operating settings, rather than average daily energy. For cycling appliances use measured kWh or actual active time and power.
What is the difference between a watt and a kilowatt-hour?
A watt is a rate of use; a kilowatt-hour is the energy that rate accumulates over time. A 1000 W device running one hour uses exactly 1 kWh.
Is the tariff required?
No. Without it you still get the consumption in kilowatt-hours, just no cost line.