Electricity Cost Calculator

How this calculator works

The math behind any electricity cost estimate is simple: watts × hours ÷ 1,000 gives you kilowatt-hours (kWh) used, and kWh × your rate (in cents per kWh, converted to dollars) gives you cost. This calculator runs that formula once for a single day, then multiplies by 30 for a monthly estimate and by 365 for a yearly one.

The state dropdown pre-fills the rate field with that state's real average residential electricity price, from our published state data (sourced from the U.S. Energy Information Administration). You can edit the rate field directly if you know your own utility's price — it's usually printed on your bill in cents per kWh, and it can run higher or lower than your state's average depending on your utility and rate plan.

Every input is saved in the page URL, so you can copy the link to share your specific numbers with someone else, or bookmark it.

What common appliances cost to run

These estimates use each appliance's published running wattage and a typical daily-use figure, priced at an illustrative rate of 17 cents/kWh — a recent U.S. average residential price, per the EIA, and not tied to any specific state. Use the calculator above with your own state's rate for a number closer to your bill.

* The security system figure comes from a single published source and reads high compared to typical residential panels (5-25W). Treat it as an upper-bound estimate, not a confirmed typical value — see the source notes in our appliance data.

Worked example

Say you run a 3-ton central air conditioner (4,000W running) for 8 hours a day during summer, in a state with a 15-cent/kWh rate. That's 32 kWh a day (4,000 × 8 ÷ 1,000), times 15 cents, for about $4.80 a day — roughly $144 a month just for cooling. Compare that to a Wi-Fi router left on 24 hours a day at 15W: about 5.4 kWh a month, or under a dollar. Wattage and hours of use matter far more than most people expect, and they usually matter more than which single device you "forget to unplug."

Common mistakes

Using nameplate wattage instead of running wattage. The number printed on a device's label is often a maximum or surge rating, not what it draws during normal operation. Using it will overstate your cost estimate, sometimes by a lot for motor-driven appliances.

Forgetting duty cycle for compressor-based appliances. A refrigerator or freezer doesn't run its compressor continuously — it cycles on and off to hold temperature. Using its full 24 hours as the "hours per day" figure will overstate cost; a rough 8-hour estimate of actual compressor run time is more realistic, which is what our reference table above uses.

Ignoring standby (phantom) load. Chargers, game consoles, and TVs often draw a few watts even when "off." It's small per device, but it adds up across a house over a full year, and it doesn't show up if you only calculate cost for the hours you're actively using something.