Electricity Cost Calculator

Running a 1,200-watt window air conditioner for 8 hours a day uses about 9.6 kWh of electricity. At the 2025 US residential average of roughly $0.17 per kWh, that works out to about $1.63 a day, near $49 a month, and close to $595 a year if you ran it every day. That single number - the gap between "it's just an AC unit" and "$595 a year" - is exactly why this electricity cost calculator exists: it turns watts and hours into real dollars so you can decide what is worth running and what is quietly draining your bill.

How the cost is calculated

The math has two simple steps - energy first, then cost:

First you find the energy used: divide the appliance's power in watts by 1,000 to get kilowatts, then multiply by the hours you use it to get kilowatt-hours (kWh) - the unit your utility bills you in. Then you multiply that energy by your rate in dollars per kWh to get the cost. 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 $0.17/kWh:

• Watts to kilowatts: 1,500 ÷ 1,000 = 1.5 kW.
• Energy per day: 1.5 kW × 6 hours = 9 kWh.
• Cost per day: 9 kWh × $0.17 = about $1.53.
• Per month: roughly $1.53 × 30 = about $46.
• Per year (if used daily): about $559.

The same heater run only 2 hours a day costs a third as much - about $0.51 a day - because cost is directly proportional to runtime.

How to use this calculator

You only need three or four numbers to get a realistic estimate:

1. Power rating (watts): read it off the appliance's label or nameplate. If it only lists amps and volts, multiply them (amps × volts = watts).
2. Hours used per day: estimate honestly. An "always-on" device like a fridge runs 24 hours; a TV might be 4-5.
3. Days: set how many days you want the total for (defaults to 30 for a month).
4. Electricity rate: use the exact $/kWh from your utility bill. If you don't have it handy, the ~$0.17 default is a reasonable US placeholder.

Tap a preset (refrigerator, AC, space heater, TV, computer, dryer) to fill typical values instantly, then press Calculate cost to see the result. The big number at the top is the monthly cost; 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 mining/AI rig running long hours.
• Renters and roommates splitting a shared bill or estimating a space heater's impact.
• 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 / vampire power: the small wattage many devices draw even when "off".
• Amps and volts: amps × volts = watts; US outlets are typically 120 V (or 240 V for large appliances).

Three quick scenarios

• Refrigerator (150 W, 24 h/day): about 3.6 kWh/day, roughly $0.61/day and near $18/month at $0.17/kWh. Always-on devices add up even at low wattage.
• LED TV (90 W, 5 h/day): about 0.45 kWh/day, roughly $0.08/day or just over $2/month - modern electronics are cheap to run.
• Clothes dryer (3,000 W, 1 h/day): 3 kWh/day, about $0.51/day or around $15/month - high wattage, but 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.

Typical wattage of common household appliances

If you cannot find a nameplate, these typical figures are a useful starting point. Actual draw varies by model, age, and setting, so confirm with the label or a plug-in meter when you can. Wattage is the maximum the device pulls when fully on; many of these cycle, so their average over a day is lower.

• Central air conditioner: 3,000-5,000 W while running - usually the single biggest line on a summer bill.
• Electric water heater: 4,000-4,500 W, but it heats in bursts rather than continuously.
• Clothes dryer: 2,000-4,000 W for the roughly hour-long cycles you run it.
• Space heater: 750-1,500 W; the high setting is exactly 1,500 W on most US models.
• Window air conditioner: 500-1,500 W depending on the BTU rating.
• Dishwasher: 1,200-1,800 W, mostly for heating water and the drying cycle.
• Microwave: 600-1,200 W, but used only minutes at a time.
• Refrigerator: 100-400 W while the compressor runs, averaging far less because it cycles - yet it runs 24/7.
• Desktop computer: 100-600 W depending on the graphics card and load; a gaming or AI rig under full load sits at the top.
• LED TV (55-inch): 60-120 W - cheap to run compared with older plasma sets.
• LED light bulb: 8-12 W each, versus 60 W for the incandescent it replaces.

Plug any of these into the fields above with your real daily hours. To size cooling or heating for a room before you estimate its running cost, the BTU Calculator gives the capacity you actually need, which keeps you from over-paying to run an oversized unit.

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 you leave it on for the full 10-hour workday. That is 1.5 kW × 10 hours = 15 kWh per day. At a $0.17/kWh rate the heater alone costs about $2.55 a day, roughly $77 a month, or close to $930 a year if you ran it every working day. Compare that with a 90 W LED desk setup running the same 10 hours: 0.9 kWh a day, about $0.15, or under $5 a month. The heater costs more than fifteen times as much. This is the classic pattern - a single high-wattage, long-hours device can quietly account for most of a seasonal bill increase, while the electronics you worry about barely register. Running the numbers tells you exactly where to cut first.

How the result is used in real life

The per-appliance cost from this tool is most useful as a decision aid, not just a number. Three common uses stand out. 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 saving tells you how quickly the upgrade pays for itself. Second, habit changes: seeing that an always-on game console or a forgotten basement freezer costs $10-$20 a 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 helps you find the culprit - usually heating, cooling, or water heating - rather than guessing. Pair the running cost with an honest hours estimate and you turn a vague "my bill is too high" into a short list of specific, dollar-ranked actions.

Why your rate - and your location - matters so much

The same appliance can cost dramatically different amounts depending on where you plug it in, because the per-kWh rate is the multiplier on everything. At the low end, several Midwest and Southern states sit near $0.11-$0.13 per kWh; at the high end, Hawaii, California, and parts of the Northeast can exceed $0.30 per kWh. A 1,500 W heater run 8 hours a day costs about $1.32 a day at $0.11 but about $3.60 a day at $0.30 - nearly three times as much for identical use. Rates also drift up over time and swing seasonally, and time-of-use plans charge a premium during peak afternoon and evening hours. Because of this spread, never rely on a national average for an important decision: pull the exact, all-in effective rate from your latest bill (total dollars divided by total kWh) and enter that. If you want to convert an appliance's amps and volts into watts before estimating its cost, the Ohm's Law Calculator handles the electrical conversion.

What changes the result the most

• Hours of use: the easiest lever - halving runtime halves the cost.
• Wattage: heaters, AC units, dryers, and ovens dominate; LEDs and small electronics barely register.
• Your rate: at $0.30/kWh, everything costs nearly double what it does at $0.16 - location matters enormously.
• Standby power: small per device, but across a whole home it can be 5-10% of the bill.

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 turning things off save money proportionally.
• Kill standby draw: use a switched power strip for electronics and chargers.
• Replace energy hogs: an old fridge 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. Your real, all-in rate also includes delivery (transmission and distribution) charges, fixed monthly service fees, and taxes. To get your effective rate, divide your total bill amount 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. If you are on a tiered plan (the rate rises after a usage threshold) or a time-of-use plan (the rate changes by hour), pick 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/time-of-use pricing.
• It assumes the device draws its rated wattage continuously while on - many appliances cycle on and off (fridges, AC, heat pumps), so real use can be lower.
• Monthly and yearly figures use a flat 30 and 365 days; it does not account for 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.

How it compares to related calculators

This page answers "what does it cost to run this appliance?" For related electrical and home questions, a sister tool fits better:

• To work out voltage, current, resistance, or power from each other, use the Ohm's Law Calculator.
• To check voltage loss over a long wire run, use the Voltage Drop Calculator.
• To size heating or cooling for a room, use the BTU Calculator.
• To measure a room or area first, use the Square Footage Calculator.

Sources

• U.S. Energy Information Administration (EIA) - Electric Power Monthly: average residential electricity prices.
• U.S. Energy Information Administration (EIA) - Energy units and calculators (watts, kilowatt-hours).
• U.S. Department of Energy (DOE) - Estimating appliance and home electronic energy use.