Appliance Energy Cost Calculator
Find the true annual running cost of any appliance from its wattage, hours of use, days per week, your electricity rate, and how many units you run — the load solar has to offset.
Last updated: May 2026
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About this calculator
An appliance's running cost is a chain of conversions, and skipping any link gives a wrong answer. Power is rated in watts, but you are billed in kilowatt-hours, so the first step divides wattage by 1,000 to get kilowatts. Energy is power times time, so you multiply by the hours used per day and then by the number of operating days in a year — expressed here as days per week times 52, which lets you model anything from a daily-use microwave to a three-day-a-week workshop tool. Multiplying kilowatt-hours by your electricity price converts energy to dollars, and multiplying by the unit count scales a single device up to a bank of them (think five identical office monitors or three space heaters). The result is the full-year cost, the figure that actually matters for budgeting and for deciding what to put on solar. Because the relationship is multiplicative, a high-wattage device used briefly can cost less than a modest device left on around the clock — a 1,500 W heater run 3 hours a day costs far less than a 50 W device running 24/7 only if you do the arithmetic, which is the whole point of computing it rather than guessing from the wattage label alone.
How to use
Worked example. You want the yearly cost of a 1,500 W space heater used 3 hours a day, every day of the week, at $0.16/kWh, and you only have one. Step 1 — convert to kilowatts: 1,500 ÷ 1,000 = 1.5 kW. Step 2 — daily energy: 1.5 kW × 3 h = 4.5 kWh/day. Step 3 — annual operating days: 7 days/week × 52 = 364 days, so 4.5 × 364 = 1,638 kWh/year. Step 4 — cost: 1,638 × $0.16 = $262.08 per year for one heater. Run two of them and it's $524.16. Knowing this number tells you the heater adds about 1,638 kWh to your annual load — roughly two extra solar panels' worth of production to offset — which is exactly how appliance cost and solar sizing connect.
Frequently asked questions
How much does it cost to run an appliance per year?
Multiply the appliance's power in kilowatts (watts ÷ 1,000) by the hours you use it per day, by its operating days per year (days per week × 52), by your electricity rate, and by how many units you run. A 1,500 W heater used 3 hours a day all week at $0.16/kWh costs about $262 a year. The same formula works for any device — just read the wattage off the nameplate or a plug-in meter. The biggest annual costs usually come from always-on or heat-producing devices: water heaters, space heaters, dryers, pool pumps, and old refrigerators.
Which household appliances use the most electricity?
Heating and cooling dominate: electric water heaters, space heaters, central air conditioning, and clothes dryers each pull 1,000–5,000 watts and run for hours, so they top most bills. Always-on loads matter too — an older refrigerator, a pool pump, or a cluster of devices on standby can quietly add hundreds of kWh a year. The way to find your own worst offenders is to compute each device's annual cost with this calculator: wattage alone is misleading because a high-watt device used briefly can cost less than a low-watt device left on continuously.
How many solar panels does it take to offset one appliance?
Convert the appliance's annual energy use to panels. The calculator's energy figure (annual cost ÷ your rate) gives kWh per year; a single modern 400 W panel produces roughly 500–650 kWh per year depending on sun. So a heater using 1,638 kWh a year needs about three panels to offset, while a 200 kWh-a-year device needs less than half a panel. This is the bridge between appliance cost and system sizing: total your big loads, convert to annual kWh, and feed that into a solar sizing calculation.