Electricity Cost Calculator

Watts vs. kilowatt-hours: the distinction that matters for your bill

Watts measure the rate of power an appliance draws at a given moment think of it like a speedometer showing miles per hour rather than the total distance traveled. Kilowatt-hours (kWh) measure actual energy consumed over time, and it's kWh, not watts, that appears on your electric bill and gets multiplied by your rate. This calculator converts between the two: watts 1,000 hours used = kWh. A 1,500W space heater run for 2 hours uses (1,500 1,000) 2 = 3 kWh the same energy a 100W bulb would take 30 hours to use.

How utility billing actually works

Once usage is converted to kWh, the cost calculation is just kWh price per kWh: 3 kWh at $0.16/kWh costs $0.48. This tool then extrapolates that daily figure to monthly (30) and yearly (365) estimates assuming the appliance runs for the same number of hours every day, which is a simplification actual usage of most appliances varies day to day. For comparison shopping, also try our free unit price calculator to identify the best value, so treat the monthly and yearly figures as a "if this pattern held steady" estimate rather than a bill prediction.

Typical appliance wattages, for context

Wattage varies enormously by appliance type. Anything that generates heat directly draws the most power: space heaters and hair dryers often run 1,000-1,500W (see also our free gas cost calculator for fuel expense estimates), electric water heaters and clothes dryers can exceed 3,000-5,000W, while a window AC unit typically falls around 500-1,500W depending on size. By contrast, electronics draw much less: a laptop is typically 30-65W, a modern LED TV 30-100W, and a phone charger just a few watts. This gap explains why running a space heater for a few hours can cost more than leaving a TV on all day heating simply takes far more energy than processing or displaying information.

Where to find an appliance's actual wattage

Check the nameplate or label on the appliance itself, its manual, or the manufacturer's product page wattage is usually printed directly. If only amps and voltage are listed instead, multiply them together (amps volts = watts), using your outlet's standard 120V in most U.S. homes (240V for larger appliances like electric dryers and ranges).

A limitation worth knowing

Understanding your utility costs helps household budgeting. Compare electricity expenses with our free paycheck calculator to see how much of your income goes to utilities. This tool uses one flat rate you enter, but many utilities charge differently depending on when or how much you use: time-of-use pricing charges more during peak afternoon and evening hours, and tiered pricing raises the rate after you cross a usage threshold for the billing period. If your plan works that way, use your average or peak rate depending on which is more relevant to when you'd run the appliance, and treat the result as a reasonable estimate rather than an exact bill figure.

FAQ

Where do I find my price per kWh?
Check a recent electric bill most utilities list a rate per kWh directly, sometimes with separate tiers or time-of-use pricing. If it's not listed plainly, divide your total bill amount by your total kWh usage for that billing period to get an effective average rate.

Does this include standby power use?
No this only calculates active running cost while the appliance is in use. Many electronics also draw small amounts of standby ("phantom") power even when switched off but still plugged in, which isn't included in this estimate.

What's the difference between watts and kilowatt-hours?
A watt measures the rate of power an appliance draws at any instant, like a speedometer reading. A kilowatt-hour measures actual energy consumed over time 1,000 watts running for one hour equals 1 kWh and it's kWh, not watts, that your utility actually bills you for.

Where do I find an appliance's wattage if it's not labeled?
Check the nameplate or label on the appliance itself, its manual, or the manufacturer's product page wattage is usually printed directly, but if only amps and voltage are listed, multiply them together (amps volts = watts) using your outlet's standard 120V in the US.

Why do heating and cooling appliances cost so much more to run than electronics?
Anything that generates heat directly space heaters, hair dryers, electric water heaters, clothes dryers draws far more wattage (often 1,000-5,000W) than electronics like a laptop or TV (typically 30-150W), because heating requires far more energy than processing or displaying information. That's why a space heater run for a few hours can cost more than a TV run all day.

Does my utility rate stay the same all day and all year?
Not always many utilities use time-of-use pricing, where electricity costs more during peak afternoon and evening hours, or tiered pricing, where the rate increases after a certain amount of usage in a billing period. This calculator uses one flat rate you enter, so if your plan varies, use your average or peak rate for the most relevant estimate.