Kilowatt-Hour (kWh) Calculator

1. Find the device wattage. Look on the label on the back or bottom of the device. It might say "1500W" or "120V, 12.5A". If you only see volts and amps, multiply them to get watts: 120V x 12.5A = 1,500W.
2. Estimate daily usage. A space heater might run 8 hours during winter evenings. A refrigerator does not draw its rated watts 24 hours a day: its compressor cycles on and off, so use the maker's annual figure where it prints one. Midea prints 207 kWh a year for its 1.6 cu. ft. compact refrigerator. A gaming PC running 6 hours a day at 350W costs differently than a laptop at 65W for 10 hours.
3. Find your electricity rate. Check your utility bill: look for "price per kWh" or "energy charge." EIA's 2025 annual U.S. residential average (EIA-861, Historical State Data) is 17.23 ¢/kWh; its 2025 state averages run from 11.82 ¢ in North Dakota to 40.40 ¢ in Hawaii, with Louisiana at 12.52 ¢ and California at 31.35 ¢. Time-of-use rates vary by hour, so use the rate that applies when the device runs. Prices and rates on this page are our own estimates as of the date shown; they change often. Enter your own figures for a current result.
4. Set the time period. The result covers the days you enter: the calculator multiplies the daily kWh by that number. A month, as a twelfth of a 365-day year, is 30.42 days, so 30 days falls a little short of a month; enter 90 for a season or 365 for a year. Seasonal devices like space heaters or pool pumps might only run 90-120 days per year.

Typical wattages are our own estimates; check your appliance's nameplate.

The big surprises are usually space heaters, EV chargers, and pool pumps. These high-watt devices running many hours per day dominate your bill. Our electricity cost calculator gives a daily, monthly, and yearly breakdown for any single appliance. A single 1,500W space heater running 8 hours a day can add nearly $60/month.

The biggest savings come from the biggest loads. Swapping a space heater for a heat pump saves 50-70% on heating energy because heat pumps move heat instead of generating it. A mini-split heat pump uses about 500W to deliver the same warmth as a 1,500W resistive heater. To project the full bill across all categories (HVAC, water heating, electronics, lighting), our electricity bill estimator builds a category-level total.

Timing matters as much as efficiency. If your electricity costs push you toward going off-grid, our solar and battery sizing calculator designs a complete system around your daily kWh usage. Even on-grid, run your dryer and dishwasher during off-peak hours if your utility offers time-of-use rates. Evening rates can be half of peak afternoon rates. A dryer load that costs $1.20 at 3pm might cost $0.60 at 9pm.

Phantom loads add up quietly. A desktop PC in sleep mode still draws 5-15W. A cable box draws 15-30W even when "off." A TV soundbar pulls 5-10W on standby. Smart power strips that cut power completely when devices are off can save 5-10% on your electronics-related energy use.

If your energy costs are high enough to justify solar panels, our solar panel output calculator shows how much of your daily kWh usage a solar array can offset. Even a modest 4-panel system can wipe out your refrigerator, lighting, and electronics usage.