Electricity Cost Calculator

The One Formula Behind Every Electricity Bill

Electricity is billed by the kilowatt hour, which is 1,000 watts drawn for one hour. Every running cost question reduces to converting watts into kilowatts, multiplying by hours, and multiplying by the rate.

Worked example. A 1,500 watt space heater running 8 hours a day at 17 cents per kWh: 1,500 divided by 1,000 is 1.5 kW, multiplied by 8 hours is 12 kWh a day, multiplied by 0.17 is 2.04 dollars a day. Over a 30 day month that is 61.20 dollars. Run all year at that rate it would be 744.60 dollars, though a heater realistically runs for only part of the year.

The Rate on the Bill

The 2026 US average residential rate is around 17 cents per kWh, but the state to state spread is enormous. Several states in the Pacific Northwest and parts of the South sit near 11 to 13 cents. California, the Northeast and Hawaii run far higher, with Hawaii typically more than double the national average. Use the number from an actual bill rather than the average.

Getting the real rate takes one step. Take the total bill amount, subtract nothing, and divide by the kWh used that month. That all-in figure includes supply, delivery, transmission, taxes and fixed fees, and it is usually 20 to 40 percent higher than the headline supply rate printed on the bill. Costs calculated on the supply rate alone understate what an appliance actually adds.

Watch for rate structures that vary:

• Tiered rates. Price per kWh rises once monthly usage passes a threshold, so extra usage costs more than average usage.
• Time of use rates. Peak periods, often late afternoon into evening, can cost two to three times the off-peak rate. Shifting a dishwasher or an EV charge to overnight is a real saving under these plans.
• Seasonal rates. Summer rates are often higher than winter rates in cooling dominated regions.
• Fixed charges. A monthly customer charge is paid regardless of usage and does not change with appliance run time.

Finding the Wattage

Nameplate wattage is usually printed on a label on the back or bottom of an appliance, on the power supply brick, or inside a door or panel. If the label shows volts and amps instead of watts, multiply them: 120 volts x 12.5 amps equals 1,500 watts.

Nameplate wattage is the maximum draw, not the average. That distinction matters most for anything that cycles or modulates.

• Cycling appliances. A refrigerator's compressor runs perhaps a third of the time. Its nameplate might read 150 watts, but it draws that only while the compressor is on. Use running hours rather than clock hours, or use the annual kWh figure from the EnergyGuide label instead.
• Variable loads. Computers, TVs and modern washers draw far less than nameplate most of the time.
• Heating elements. Space heaters, toasters, kettles and hair dryers draw essentially full nameplate whenever they are on, which makes them the easiest to calculate and often the most expensive per hour.
• Motors. Starting current is much higher than running current, but the surge is too brief to matter for cost.

For anything uncertain, a plug-in energy meter measures actual kWh over a week and removes the guesswork entirely.

Standby and Vampire Load

Devices that appear off often are not. Anything with a remote control, a clock, a standby light, a network connection or an external power brick draws power continuously. Individually these loads are trivial. Collectively they typically account for around 5 to 10 percent of a residential bill.

A single device drawing 3 watts continuously uses 26 kWh a year, about 4.47 dollars at 17 cents. Multiply that by the 30 to 50 always-on devices in a typical modern home and the total lands somewhere between 50 and 200 dollars a year. The worst offenders are set top boxes and DVRs, which can draw 15 to 30 watts around the clock, older game consoles left in an instant-on state, and desktop computers left asleep rather than shut down.

The practical fix is a switched power strip for clusters of entertainment or office equipment, and unplugging chargers and secondary devices that are used rarely. Chasing 1 watt phone chargers is not worth the effort.

What Actually Dominates a Bill

Four categories account for the large majority of residential electricity use, and everything else competes for the remainder.

• Heating and cooling. Usually the single largest share, often 40 percent or more in homes with electric heat or heavy air conditioning. Central AC and electric resistance heat are the biggest individual loads in most homes.
• Water heating. Frequently the second largest, commonly 12 to 18 percent. An electric water heater element is 4,500 watts and runs a few hours a day of accumulated time.
• Laundry and dishwashing. Electric clothes dryers are 3,000 to 5,000 watts. Most of a washing machine's and dishwasher's cost is heating water, not turning the drum.
• Refrigeration. A modern refrigerator uses 350 to 500 kWh a year. A second refrigerator or a chest freezer in a garage, often 15 or 20 years old, can use as much again.

Lighting used to belong on that list and no longer does. A whole house converted to LED typically spends less on lighting than on a single old chest freezer.

Appliance Running Cost Reference Table

Typical wattages and annual costs at 17 cents per kWh. Hours per year reflect common usage patterns, including seasonal appliances that run only part of the year.

Refrigerator hours are compressor running hours, not clock hours, which is why the figure is 2,920 rather than 8,760. Water heater and air conditioning hours are accumulated element or compressor time across the year.

Reading the Result Correctly

Three habits keep these estimates honest. First, use realistic hours. A heater that runs 8 hours a day for 90 days costs a quarter of what it would running all year. Second, use average draw for anything that cycles, or work from the annual kWh on the EnergyGuide label. Third, remember that fixed monthly charges do not scale with usage, so cutting consumption by 20 percent does not cut the bill by 20 percent.

These are estimates. Actual costs depend on the specific model, its age and condition, ambient temperature, thermostat settings, insulation and the utility's rate structure. A plug-in meter or a whole home energy monitor gives measured numbers where an estimate is not good enough.