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Electricity Cost Calculator

Use this electricity cost calculator to estimate appliance energy use and cost from watts, hours per day, days used, and cents per kWh.

Last reviewed June 6, 2026Source note includedFree tool

Live calculator

Electricity cost

Estimated cost$24.30

135 kWh over 30 days.

Daily cost$0.81

Average cost per day for the usage pattern.

30-day estimate$24.30

Daily cost scaled to a 30-day month.

Utility estimates depend on local rates, fixed fees, taxes, runtime, billing period, and household usage. Compare against the actual bill before settling up.

Quick answer

Electricity Cost Calculator: what it calculates

Electricity Cost Calculator calculates electricity cost from watts, hours per day, days, and electricity rate. The visible formula is Cost = watts / 1000 x hours per day x days x electricity rate per kWh.

ResultElectricity cost
InputsWatts, Hours per day, Days, Electricity rate
FormulaElectricity cost formula

Formula

Electricity cost formula

Cost = watts / 1000 x hours per day x days x electricity rate per kWh

Use the wattage listed on the device or a measured average. Actual energy use can vary by setting and duty cycle.

How to use

Steps

  1. Enter the appliance wattage.
  2. Enter how many hours per day it runs.
  3. Enter the number of days to estimate.
  4. Enter your electricity rate in cents per kilowatt-hour.

Example

Sample calculation

Watts1,500
Hours/day3
Rate18 cents/kWh
30-day cost$24.30

Calculator use

Best for

  • Use this electricity cost calculator to estimate appliance energy use and cost from watts, hours per day, days used, and cents per kWh.
  • Estimating home utility cost, shared bills, appliance usage, or service charges before splitting or budgeting.
  • Testing usage changes such as shorter showers, different appliance cycles, rate changes, or roommate shares.
  • Keeping rate, meter, usage, and fixed-fee assumptions visible before comparing against a real bill.

Before relying on it

Check first

  • Leaving out fixed service fees, tiered rates, taxes, delivery charges, minimum bills, seasonal rates, or billing-period length.
  • Using appliance labels, averages, or old bills without checking actual runtime, local rates, and household usage.
  • Splitting a bill without agreeing whether fixed fees, shared rooms, guests, or unequal usage should be weighted.

Details

What to know before using the result

These notes make the assumptions explicit, especially where the same search query can mean slightly different things.

Power to energyWatts x hours

Watts measure power at a moment. Multiplying by time estimates energy use, which electric bills usually express in kilowatt-hours.

Duty cycleActual use can vary

Devices like refrigerators, heaters, air conditioners, and chargers may cycle on and off instead of using rated wattage continuously.

Rate inputUse your bill's kWh rate

Electric bills can include delivery charges, time-of-use pricing, fees, and taxes, so the effective rate may differ from the headline energy charge.

Source notes

References used for this calculator

U.S. Energy Information AdministrationExplains watts, watthours, and kilowatt-hours with examples of power used over time.U.S. Department of EnergyShows the appliance energy cost formula and notes that actual wattage can vary by product and usage.

Benchmarks

How to read the result

The calculator is a decision aid, not a fixed rule. Use the output to compare scenarios and document your assumptions. Benchmark ranges are broad planning heuristics unless this page names a specific source for the range.

Under 100W: Low draw.

Common for LED bulbs, chargers, small fans, and efficient electronics.

500W - 1,500W: Medium to high draw.

Common for space heaters, microwaves, hair dryers, and kitchen appliances.

Runs many hours: Cost adds up.

Low wattage devices can still cost more when they run all day.

Calculator accuracy

Methodology and assumptions

The formula, inputs, example, and limitations are shown so the result is checkable, not just a number in a box.

Formula

Cost = watts / 1000 x hours per day x days x electricity rate per kWh

Inputs used

Watts, Hours per day, Days, Electricity rate

Limitations

Utility pages use visible usage and rate assumptions. Actual bills may include tiers, service fees, delivery charges, taxes, minimums, seasonal rates, and provider-specific rules.

Last reviewed

June 6, 2026

Cite this page

Toolkit Shelf. Electricity Cost Calculator. Last reviewed June 6, 2026. https://toolkitshelf.com/tools/electricity-cost-calculator

FAQ

Common questions

How do I calculate appliance electricity cost?

Divide watts by 1,000 to get kilowatts, multiply by hours used, then multiply by your cost per kWh.

What is a kilowatt-hour?

A kilowatt-hour is 1,000 watts used for one hour. Electric bills usually charge by kWh.

Why is the result only an estimate?

Many devices cycle on and off or use different power levels, so listed wattage may not equal average wattage.

Why might the real-world result differ?

Match the result to the task type: shopping tools depend on the same unit and usable quantity, home-project tools depend on field measurements and waste, date/time tools depend on counting rules, and conversion tools depend on the unit system.

Should I round the result?

Round for readability after checking the formula and units. Keep more precision when the result feeds another calculation, and add a task-specific buffer only when shortage, waste, or timing risk matters.

Why might another calculator show a different output?

Different tools may use different rounding, assumptions, default rates, methods, formulas, or input timing. Compare the visible method and inputs before relying on the output.