Free Online Electricity Calculator

This electricity calculator works out how much power an appliance actually uses and what that costs you per day, week, month and year. Pick a common appliance to auto-fill typical numbers, or type in your own for a more accurate electricity cost calculator result.

Looking for something else? Explore more free tools in our Horsepower Calculator, Numbers to Words Converter and Ratio Calculator — or browse our full calculator library to find exactly what you need.

Electricity Calculator

% capacity
Most appliances rarely run at full power the whole time — e.g. an AC or oven cycles on and off to hold a temperature.
$ per kWh

Typical Appliance Wattage

These ranges are a rough guide — actual draw depends heavily on the specific model.

ApplianceEstimated Wattage
Air conditioner (HVAC)2,500–10,000 W
Refrigerator500–1,000 W
Electric range/oven2,000–5,000 W
Microwave oven750–1,500 W
Clothes dryer1,800–5,000 W
Television25–500 W
Laptop computer35–150 W
LED light bulb3–25 W

Result

Time SpanUsageCost

Assumes 30.44 days per month and 365.25 days per year on average.

Your estimated electricity usage and cost will appear here once you calculate.

How This Electricity Calculator Works

Your electric bill isn't based on how powerful an appliance is — it's based on how much energy it actually uses over time. A 1,000-watt heater left running for one hour uses the same energy as a 100-watt bulb left on for ten hours. That's the whole idea behind the kilowatt-hour (kWh), the unit your power company actually bills you for.

The Formula

Daily Energy (kWh) = Power (kW) × Capacity % × Hours Used per Day

From there, weekly, monthly and yearly figures are just that daily number scaled up, and the cost is simply that energy multiplied by your price per kWh.

Worked Example

A 1,000W appliance, run at 100% capacity for 24 hours a day, with electricity priced at $0.15/kWh:

Daily: 1 kW × 1.0 × 24 = 24 kWh → 24 × $0.15 = $3.60
Weekly: 24 × 7 = 168 kWh → $25.20
Monthly: 24 × 30.44 = 730.6 kWh → $109.58
Yearly: 24 × 365.25 = 8,766 kWh → $1,314.90

Why "Capacity" Matters

The wattage printed on an appliance is usually its maximum draw, not what it actually pulls most of the time. An air conditioner cycles its compressor on and off to hold a temperature, a fan is rarely run flat out, and an oven only fires its heating element in bursts once it's up to temperature. That's what the "capacity" field is for — a rough estimate of how much of that maximum power gets used on average.

Converting Other Power Units

Not every appliance lists its power in watts. Here's how the common ones convert:

  • Kilowatt (kW): 1 kW = 1,000 W
  • BTU/hour: 1 BTU/h ≈ 0.2931 W
  • Metric horsepower (hp): 1 hp ≈ 735.5 W
  • Ton (refrigeration): 1 ton ≈ 3,517 W

Simple Ways to Cut Your Electricity Bill

  • Swap older incandescent bulbs for LEDs — they use roughly a tenth of the power for the same brightness.
  • Use a programmable thermostat, or just get into the habit of adjusting it manually through the day.
  • Unplug or use a smart plug for devices that draw power even when "off," like TVs and game consoles on standby.
  • Check for drafts around windows and doors — heating and cooling lost through gaps is money straight out the window.
  • Run big appliances like dishwashers and washing machines with full loads instead of half-full ones.

Frequently Asked Questions (FAQs)

Watts measure the rate of power an appliance draws at any given moment, while kilowatt-hours measure the total energy used over time. A 100W bulb running for 10 hours uses exactly 1 kWh, the same amount of energy as a 1,000W appliance running for just 6 minutes.

Check the label or nameplate on the appliance itself, usually on the back or bottom, or in its manual. If it only lists amps and volts, multiply the two together to get watts (Watts = Amps × Volts).

This is almost always a capacity or usage-hours overestimate. Most appliances don't run at their rated wattage the entire time they're switched on, so lowering the capacity percentage or usage hours to better match reality will bring the estimate closer to what you actually see billed.

Check a recent electricity bill — most utilities list a per-kWh rate directly, though some charge tiered rates that increase the more you use, or add flat fees on top. For a rough estimate, dividing your total bill amount by your total kWh usage for that period works too.

Yes — run the calculation once for each appliance with its own power, capacity and usage figures, then compare the yearly cost lines side by side. This is a handy way to see, for example, whether upgrading an old fridge to a more efficient one is actually worth it.
Disclaimer: This calculator gives a general estimate based on the values you enter and average day/month/year lengths. Actual usage varies by appliance model, condition and habits, and actual electricity bills often include additional fees, taxes or tiered pricing not reflected here. Check your utility provider for your exact rate structure.

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