Electricity use & cost calculator
Turn device power and a usage schedule into energy and cost—keeping the entered tariff and daily standing charge visibly separate.
Constant power, usage and entered tariff only. No tariff bands, taxes, demand charges, cycling, standby or bill prediction.
Included
- Constant device power in W or kW and a quantity of identical devices
- Hours per use and number of uses per day, week or month
- User-entered price per kWh and optional daily standing charge
- Energy and cost per selected period plus annual equivalent
Not included
- Time-of-use bands, tiered tariffs, taxes and demand charges
- Standby cycles, changing power, efficiency curves and measured usage
- Bill prediction or tariff recommendation
What this means
Energy is power multiplied by time. The calculator first converts the entered device power to kilowatts, multiplies by quantity and hours per use, then expands the entered daily, weekly or monthly usage schedule to a year.
The selected-period energy charge is kWh multiplied by the tariff you enter. A daily standing charge is scaled by calendar days and shown separately before the two amounts are added.
This is a constant-input model. A rated device may cycle, draw standby power or operate below its label rating, so a plug-in energy meter can provide a better usage input when accuracy matters.
Formula & worked example
kWh per use = power in kW × quantity × hours annual kWh = kWh per use × uses per basis × bases per year energy charge = period kWh × entered tariff standing charge = entered daily charge × days in period total cost = energy charge + standing charge
Two 1 kW devices, 3 hours per use, 4 uses per week, tariff 0.30/kWh and standing charge 0.50/day
- Energy per use
- 1 kW × 2 × 3 h = 6 kWh
- Annual energy
- 6 kWh × 4 × 52 = 1,248 kWh
- Annual energy charge
- 1,248 × 0.30 = 374.40
- Annual standing charge
- 0.50 × 365 = 182.50
The estimated annual total is 556.90 before any unentered taxes, tariff bands or other bill items.
How this calculation works
The calculation follows the formulas, definitions and assumptions explained on this page. The references below support the method and any stated boundaries.
Official sources
- U.S. Energy Information Administration — measuring electricity — Watts and kilowatts measure power; watt-hours and kilowatt-hours measure energy used over time
- U.S. Energy Information Administration — kilowatthour definition — One kWh is one kilowatt of power expended for one hour