Electricity Cost Calculator

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How to Use the Electricity Cost Calculator

1. 1

   Add an appliance

   Type a name and wattage, or pick from the preset list (LED bulb, refrigerator, air conditioner, dryer and others) to fill the wattage automatically.

2. 2

   Enter hours per day and quantity

   Hours is average daily runtime, not how long it is plugged in. Quantity multiplies the same appliance — six identical bulbs is one row with quantity 6.

3. 3

   Set your rate and billing days

   Enter the cost per kWh from your utility bill. The default is $0.12. Billing days defaults to 30; change it if your billing period differs.

4. 4

   Add the rest and read the breakdown

   Add a row per appliance. Results update as you type: total watts, kWh per day, monthly kWh and cost, yearly cost, and each appliance ranked by what it costs you.

How electricity cost is calculated

Electricity is billed by the kilowatt-hour: one kilowatt (1,000 watts) drawn for one hour. A 100 W device left on for 10 hours uses exactly the same 1 kWh as a 1,000 W device run for one hour.

The yearly figure here is the monthly cost times 12, using your billing-days setting. It is not multiplied by 365, so a 30-day month gives a 360-day year — close enough for planning, and it keeps the yearly figure consistent with the monthly one you can check against a bill.

Daily kWh = watts × hours per day × quantity ÷ 1,000
Monthly kWh = daily kWh × billing days
Monthly cost = monthly kWh × rate per kWh
Yearly cost = monthly cost × 12

Worked example: a space heater through winter

Run it in two rooms and the quantity field doubles everything: 450 kWh and $67.50 a month. This is why a single high-wattage appliance usually beats every light bulb in the house combined — the heater above costs more per month than 30 LED bulbs running 5 hours a day.

• A 1,500 W space heater, run 5 hours a day, at $0.15 per kWh.
• Daily: 1,500 × 5 ÷ 1,000 = 7.5 kWh.
• Monthly (30 days): 7.5 × 30 = 225 kWh.
• Monthly cost: 225 × $0.15 = $33.75.
• Yearly if run all year: $33.75 × 12 = $405.

What common appliances cost to run

Monthly figures below use the calculator defaults: 30 billing days, at $0.15 per kWh. Wattages are the presets built into the tool; check the label or nameplate on your own appliance, since a 2,000 W hair dryer costs twice what a 1,000 W one does.

Why your bill may not match

• A refrigerator does not draw its rated wattage continuously — the compressor cycles. Entering 150 W for 24 hours overstates it. For a closer figure, enter the rated watts for roughly 8 hours a day instead, or use the annual kWh printed on the energy label divided by 365.
• Anything that heats or cools on a thermostat behaves the same way: air conditioners, space heaters, ovens and water heaters all cycle rather than run flat out.
• Utility bills include fixed charges, delivery fees and taxes on top of the per-kWh rate. Divide your total bill by the kWh used to get your real all-in rate, then use that here.
• Many utilities charge tiered or time-of-use rates, so the last kWh of the month can cost far more than the first. A single average rate will understate a heavy month.
• Standby draw is invisible here. A device pulling 2 W around the clock is 1.4 kWh a month on its own — small individually, but a house with 20 of them loses around $4 a month at $0.15.

Finding an appliance wattage

• Check the nameplate or sticker, usually on the back or underside. It lists watts, or volts and amps.
• If it lists volts and amps instead, multiply them: 120 V × 5 A = 600 W.
• The energy label on large appliances gives estimated annual kWh, which is more accurate than a nameplate because it accounts for cycling.
• A plug-in energy monitor measures actual draw and settles the question for anything that cycles or has several modes.
• Nameplate wattage is the maximum, not the average. A laptop rated 65 W might average 20 W browsing.

Features

• kWh consumption calculation
• Cost estimation
• Multiple appliance support
• Monthly/yearly projections

Frequently Asked Questions