How to Calculate What Any Appliance Actually Costs to Run
By the Super Simple Digital Tools Team · Updated June 2026
Your electricity bill is really just one number measured over and over: the kilowatt-hour. A kilowatt-hour is what you use when a 1,000-watt device runs for one hour. Everything on your bill, the fridge, the dryer, the always-on router, gets boiled down to how many of those kWh it consumed, multiplied by a price. Once you understand that single unit, the cost of any appliance stops being a mystery and becomes a quick multiplication you can do in seconds.
Start by finding three numbers. First, wattage, which is usually printed on the appliance's nameplate, sticker, or in the manual; if you only see amps and volts, multiply them together (a 10-amp device on a 120-volt circuit is 1,200 watts). Second, the hours it runs in a typical day. Third, your rate per kWh, copied from your utility bill. With those three values the calculator handles the conversions, but it helps to know what it's doing under the hood.
The formula has two steps. Convert watts to kilowatts by dividing by 1,000, then multiply by hours to get energy used: a 1,500-watt heater for 8 hours is 1.5 kW x 8 = 12 kWh. Then multiply energy by your rate to get cost: 12 kWh x $0.17 = $2.04 per day. From there, scaling up is easy: multiply by 30 for a monthly estimate (about $61) or by 365 for the yearly figure (about $745). The same two steps work for a phone charger or a hot tub.
The biggest source of error isn't the math, it's the wattage assumption. Listed wattage is the maximum a device can draw, but many appliances don't run flat-out the whole time. A refrigerator's compressor cycles on and off, an air conditioner modulates, and a washing machine only heats water during part of its cycle. For these, your real-world cost is lower than a constant-wattage estimate, so treat such results as a sensible upper bound rather than an exact number.
To turn estimates into action, focus on the two levers you control: wattage and time. A device that's both high-wattage and runs for many hours, such as electric heating, water heating, or an EV charger, dominates your bill, so even small efficiency gains there pay off. Low-wattage gadgets matter mostly in aggregate through standby power, which can quietly add up across a whole house. Pricing each one with the calculator shows you exactly which battles are worth fighting.
- Read your rate straight off the bill and include per-kWh delivery and supply charges, not just the advertised rate, for a truer cost.
- For cycling appliances like fridges and ACs, treat the calculator's number as a maximum and expect your real cost to be somewhat lower.
- Borrow or buy a plug-in energy monitor (around $25 to $50) to measure a device's actual watts instead of guessing from the label.
- If you're on a time-of-use plan, run high-wattage devices during off-peak hours and re-run the calculation with the off-peak rate to see the savings.