Electricity Cost Calculator

To calculate electricity cost, multiply an appliance's wattage by the hours you use it, divide by 1,000 to get kilowatt-hours, then multiply by your price per kWh. A 1,500-watt space heater run 6 hours a day uses 9 kWh, which costs about $1.65 a day, $49.44 a month or $601.48 a year at the U.S. average residential price of 18.31 cents per kWh (EIA, July 2026). Those are the calculator's starting values, so you can change one input at a time and watch the cost move.

The calculator handles one appliance at a time. To find how big a heating or cooling unit should be before you estimate its running cost, start with the BTU Calculator; to turn a nameplate's watts into the current it draws, use the Watts to Amps Calculator; and to estimate what panels could offset, see the Solar Panel Calculator.

How the cost is calculated

The math has two steps, energy first and then cost. It is the same method the U.S. Department of Energy publishes for estimating appliance energy use:

First you find the energy used: multiply the appliance's power in watts by the hours it runs each day and divide by 1,000 to get kilowatt-hours (kWh), the unit your utility bills you in. Then multiply that energy by your price in dollars per kWh. The calculator scales the daily figure to 30 days for a monthly estimate and 365 days for a yearly one.

A worked example, step by step

Take a 1,500-watt space heater run 6 hours a day at 18.31 cents per kWh:

The same heater run only 2 hours a day costs a third as much, about $0.55 a day, because cost is directly proportional to runtime.

How to use this calculator

1. Power rating (watts): read it off the label or nameplate. If it only lists amps, multiply amps by volts.
2. Hours used per day: estimate honestly. For an appliance that cycles, such as a refrigerator, the DOE suggests using about a third of the hours it is plugged in.
3. Days: how many days you want the total for (30 by default).
4. Electricity rate: enter the price per kWh from your bill. If you do not have it, the default is the latest U.S. average (18.31 cents, July 2026).

Or tap a preset (refrigerator, window AC, space heater, TV, computer, dryer) to fill example values. The result updates as you type: the big number is the monthly cost, and the cards and table below break out energy and cost per day, month, year and your chosen number of days.

Who this calculator is for

• Homeowners and renters trying to find what is driving a high electric bill.
• Bargain hunters deciding whether an energy-hungry old appliance is worth replacing.
• Remote workers and gamers sizing the cost of a desktop, monitors or a computer that runs long hours.
• Roommates splitting a shared bill or estimating a space heater's share.
• Small businesses estimating the running cost of equipment, signage or refrigeration.

Key terms explained

• Watt (W): the rate of power draw at any instant. 1,000 watts = 1 kilowatt (kW).
• Kilowatt-hour (kWh): energy used over time; 1 kW running for 1 hour. This is what you are billed for.
• Rate ($/kWh): the price your utility charges per kilowatt-hour, found on your bill.
• Standby or "phantom" load: the small power many devices draw even when switched off.
• Amps and volts: amps × volts = watts. Most U.S. outlets are 120 V; large appliances use 240 V.

Three quick scenarios

• Refrigerator (150 W, counted as 8 h/day): 1.2 kWh a day, about $0.22 a day and $6.59 a month at 18.31 cents. Always-on devices add up even at low wattage.
• LED TV (90 W, 5 h/day): 0.45 kWh a day, about $0.08 a day or $2.47 a month.
• Clothes dryer (3,000 W, 1 h/day): 3 kWh a day, about $0.55 a day or $16.48 a month: high wattage, but a short runtime keeps the total moderate.

The pattern is clear: wattage × hours together decide the cost. A low-watt device left on all day can cost more than a high-watt device used briefly.

How to find an appliance's wattage

The DOE lists several ways to get the number you need:

• The nameplate: the wattage stamped on the back or bottom is the maximum power the appliance draws. Devices with settings (fan speeds, volume, heat levels) often draw less.
• Amps times volts: if only amps are listed, multiply by 120 V for most appliances or 240 V for large ones such as clothes dryers and electric cooktops.
• A plug-in usage monitor: measures the actual watts and kWh of any 120 V device over hours or days, including cycling and standby. It cannot be used on 240 V appliances.
• The EnergyGuide label: the yellow label on new appliances lists estimated yearly energy use in kWh, which you can multiply directly by your rate.
• Cooling equipment: electrical draw is roughly the cooling capacity in BTU/h divided by the efficiency rating (EER); the BTU Calculator explains how.

How much does it cost to run an appliance per day, month and year?

This matrix runs the formula for example appliances at the U.S. average price of 18.31 cents per kWh (July 2026). The wattages and hours are illustrations, not measured averages; swap in your own label figures and rate above. Notice how high-wattage, long-hours devices dominate the yearly column.

Monthly = 30 days, yearly = 365 days, rounded. Appliances that cycle (air conditioners, water heaters, refrigerators) only draw full power part of the time, which is why the hours column is lower than the hours they are switched on.

A second worked example: finding a hidden energy hog

Imagine your bill jumps in winter and you suspect a space heater in a home office. The heater is rated 1,500 W and runs for the full 10-hour workday. That is 1.5 kW × 10 hours = 15 kWh per day. At 18.31 cents per kWh the heater alone costs about $2.75 a day, roughly $82 a month of daily use, or about $687 over 250 working days a year. Compare that with a 90 W LED desk setup running the same 10 hours: 0.9 kWh a day, about $0.16, or under $5 a month. The heater costs more than fifteen times as much. That is the usual pattern: one high-wattage, long-hours device can account for most of a seasonal bill increase, while the electronics people worry about barely register.

How the result is used in real life

The per-appliance cost is most useful as a decision aid. First, replace-or-keep decisions: if an old refrigerator costs $25 a month to run and a new efficient one would cost $8, the $17 monthly difference tells you how quickly the upgrade pays for itself; the EnergyGuide labels give you both models' yearly kWh. Second, habit changes: seeing that an always-on second freezer or an idle game console costs real money each month makes it easy to justify unplugging it or putting it on a timer. Third, budgeting and bill disputes: when your bill spikes, estimating each major appliance's share points you to the culprit, usually heating, cooling or water heating, instead of guessing.

Electricity prices by state: why your rate matters so much

The price per kWh multiplies everything, and it varies more than threefold across the country. In July 2026 the EIA's Electric Power Monthly reported average residential prices of 12.72 cents in Louisiana, 12.77 in Nevada and 13.12 in Utah at the low end, and 30.49 cents in Massachusetts, 32.41 in Maine, 33.61 in California and 48.00 cents in Hawaii at the high end, against a U.S. average of 18.31 cents. A 1,500 W heater run 8 hours a day costs about $1.53 a day in Louisiana but $5.76 a day in Hawaii, nearly four times as much for identical use. Prices also change from month to month and many utilities charge more at peak times, so for an important decision use the all-in effective rate from your latest bill (total dollars divided by total kWh). To convert an appliance's amps and volts into watts first, the Ohm's Law Calculator handles the electrical conversion.

Electricity cost per kWh: how much your rate changes the bill

This quick reference shows the monthly cost at each price for three example devices, plus what a single kWh costs. Enter your own bill's effective rate above for a precise result.

Monthly figures assume 30 days at the stated hours. State rates are EIA averages for July 2026; your utility's rate and fees may differ.

What changes the result the most

• Hours of use: the easiest lever, since halving runtime halves the cost.
• Wattage: heaters, air conditioners, dryers and ovens dominate; LEDs and small electronics barely register.
• Your rate: at Hawaii's 48.00 cents, everything costs nearly four times what it does at Louisiana's 12.72 cents.
• Standby power: small per device, but Lawrence Berkeley National Laboratory puts it at 5 to 10% of residential electricity use.

Tips to cut your electricity cost

• Target high-watt, long-hours devices first: heating and cooling usually lead the bill.
• Reduce runtime: timers, thermostats and simply switching things off save money in direct proportion.
• Cut standby draw: the DOE suggests unplugging idle devices or using a power strip and switching it off.
• Replace energy hogs: compare EnergyGuide labels; an old refrigerator or incandescent bulbs can pay back an upgrade quickly.
• Shift usage to off-peak hours if you are on a time-of-use plan.

Reading your electricity rate from the bill

Utility bills can be confusing because the per-kWh "energy charge" is only part of the price. The all-in rate also includes delivery (transmission and distribution) charges, fixed monthly service fees and taxes. To get your effective rate, divide the total bill by the total kWh used that month; that single number is the best figure to enter here, because it reflects what each extra kilowatt-hour actually costs you. On a tiered plan (the rate rises after a usage threshold) or a time-of-use plan (the rate changes by hour), use the rate that matches when and how much the appliance runs.

Limitations and assumptions

• It estimates one appliance at one flat rate; it does not sum your whole home or model tiered or time-of-use pricing.
• It assumes the device draws its rated wattage for every hour you enter; for appliances that cycle, enter the hours they actually run (the DOE's one-third rule for refrigerators).
• Monthly and yearly figures use a flat 30 and 365 days and ignore seasonal patterns.
• Standby power, fixed charges, fees and taxes are excluded unless you build them into your rate.
• It does not model solar generation or net metering; it shows gross grid cost only.

Related calculators

• To size an air conditioner before you estimate its running cost, use the BTU Calculator.
• To convert watts into amps for a circuit, use the Watts to Amps Calculator.
• To work out voltage, current, resistance or power from each other, use the Ohm's Law Calculator.
• To estimate how much of the bill solar panels could cover, use the Solar Panel Calculator.

Sources

• U.S. Energy Information Administration: Electric Power Monthly, Table 5.6.A, average residential price by state, July 2026 (U.S. 18.31 cents per kWh; released September 24, 2026).
• U.S. Energy Information Administration: Electric Power Monthly, Table 5.3, monthly and annual U.S. averages (residential: 17.45 cents in July 2025, 17.30 cents for 2025).
• U.S. Department of Energy, Energy Saver: Estimating appliance and home electronic energy use (the kWh formula, nameplate wattage, amps times volts, the one-third rule for refrigerators, usage monitors).
• Lawrence Berkeley National Laboratory: Standby Power (standby loads are 5 to 10% of residential electricity use).
• U.S. Energy Information Administration: Energy units and calculators (watts and kilowatt-hours).