Watt and Wall

Energy calculator

Electricity Cost Calculator for kWh and Device Use

Convert a known kWh total into cost, or estimate daily, monthly, and annual electricity use from device power, usage time, and your local rate.

Your values

Calculate electricity cost

Use a known kWh total or estimate energy from power and usage time. All visible fields are required.

Choose known kWh for a bill, meter reading, or product energy estimate.

Power and usage inputs

Use the device label or a measured average.

1 kW equals 1,000 W.

Maximum 24 hours. Decimals are allowed.

Enter a whole number from 1 to 31.

Electricity rate and currency

Use the applicable variable price per kWh from your bill or tariff. Do not include fixed monthly fees.

Changes the label only. Enter a rate in this currency; no exchange conversion occurs.

Live estimate

Estimated energy and cost

Updated estimate: $21.60 per month and $259.20 per year.

Estimated monthly cost

$21.60

Example currency format; based on 30 active days

Per active day
$0.724.5 kWh
Per month
$21.60135 kWh
Per year
$259.201,620 kWh

Planning estimate only. Fixed fees, taxes, tariff rules, and unlisted electricity use can change your bill.

Transparent calculation

kWh cost formula and power formula

If you already know the energy total, multiply kWh by the applicable local rate. If you know device power instead, calculate kWh from power and usage time first.

Known-energy cost = kWh × local-currency price per kWh

Power in kW = watts ÷ 1,000

Active-day energy = power in kW × hours

Monthly energy = active-day kWh × active days

Cost = energy in kWh × local-currency price per kWh

Annual estimate = monthly estimate × 12

Worked examples

At the US average residential rate of $0.1834/kWh for June 2026, 410 kWh costs $75.19. This is a dated national reference. Your bill or tariff provides the rate for your location and plan.

410 kWh × $0.1834/kWh = $75.19

For a 1,500 W device used 3 hours on 30 days each month at $0.16/kWh:

Active day
4.5 kWh · $0.72
Month
135 kWh · $21.60
Year
1,620 kWh · $259.20

Electricity cost questions

Choose Known energy use, enter the kWh total from your bill, meter, or product estimate, and enter the applicable price per kWh. The calculator multiplies those two values. Fixed fees and tariff adjustments remain outside the result.