PowerCalcLab

Power calculator

Appliance Energy Cost Calculator

Estimate energy and cost for appliances that run continuously, cycle on and off, or consume standby power. Enter your own all-in energy rate and comparison period.

Use the marginal or all-in per-kWh rate you want to compare; do not include fixed monthly charges.

Advanced assumptions

Results update as you type. The calculator runs entirely in your browser — nothing you enter is sent anywhere.

Estimated cost for 30 days$16.32

Calculation breakdown

Daily energy3.022 kWh/day
Period energy90.66 kWh
Standby energy22 modeled standby hours per day0.022 kWh/day
Annualized energy1,103 kWh/year
Annualized cost$198.55
Cost = [(running W × active h + standby W × standby h) × quantity ÷ 1,000] × days × rate/kWh
= [( 1500 × 2 + 1 × 22) × 1 ÷ 1,000] × 30 × 0.18
= 90.66 kWh × $0.18/kWh = $16.32
  • Duty cycle converts scheduled time into equivalent full-power running hours. Standby is applied during the remaining hours of each 24-hour day.
  • Use a measured average wattage for cycling or variable-speed appliances when possible. Nameplate input can overstate or understate typical energy.
  • Enter the marginal energy rate you want to model. Fixed monthly charges and demand charges are not allocated to one appliance.

Method

How the number is reached

Running watts are multiplied by equivalent active hours. Duty cycle is used for thermostatic, compressor and other cycling loads; standby watts apply during the remaining hours of the day.

Watt-hours are divided by 1,000 for kWh and multiplied by the user-entered energy rate. The same daily model is annualized for comparison without changing the tariff.

Active h/day = scheduled h/day × duty cycle
Daily kWh = [(running W × active h) + (standby W × remaining h)] × quantity ÷ 1,000
Period cost = daily kWh × days × rate/kWh

Symbols

kWh
Kilowatt-hour of electrical energy
Duty cycle
Share of scheduled time at running power

Worked examples

The same maths, applied

Example

1,500 W appliance used two hours daily

One appliance runs at full duty, draws 1 W in standby, is modeled for 30 days, and electricity costs $0.18/kWh.

Active energy = 1,500 × 2 = 3,000 Wh/day
Standby energy = 1 × 22 = 22 Wh/day
Period energy = 3.022 × 30 = 90.66 kWh
Cost = 90.66 × $0.18 = $16.32

Result: $16.32 for 30 days.

Limits of the model

What it assumes, and where it stops

Assumptions

The entered watts and duty cycle represent average behavior for the modeled period.

Not covered

Does not model time-of-use tiers, demand charges, taxes, minimum bills or fixed monthly charges.

Sources

Where these figures come from

  • EnergySavers: Tips on Saving Money and Energy at HomeU.S. Department of EnergyGovernment consumer guidance defining watt-hours and kilowatt-hours and explaining that utility bills charge for kWh used.
  • Measuring Standby PowerU.S. Department of EnergyGovernment guidance explaining that plugged-in devices may consume standby power even when they appear off.
  • SI UnitsNIST Office of Weights and MeasuresDefinitions of the volt, ampere, watt and joule used for the unit conventions on this site.

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Last meaningful update: 2026-08-19. This date changes only when the model, the sources or the guidance change.