Appliance Cost Calculator

Appliance labels state power or annual energy under test conditions, but actual cost depends on runtime and local price. Choose an air conditioner, hot tub, dehumidifier, or another preset, then replace the planning wattage with measured power when possible.

The calculation converts watts to kilowatts and multiplies by operating hours. For equipment controlled by a thermostat, runtime means compressor or heater-on time, not simply the hours it is plugged in.

Hot-tub heating varies with outdoor temperature, cover quality, setpoint, wind, and use. Air-conditioner demand depends on heat, humidity, insulation, sizing, and efficiency. Dehumidifiers cycle to maintain a humidity target.

A plug-in energy meter can measure 120 V appliances directly. For hardwired 240 V loads, use utility interval data or a properly installed monitoring device rather than opening energized equipment.

Assumptions and edge cases

Preset wattages are planning values for typical residential equipment, not measurements of your unit, and the runtime field means the hours the appliance actually draws power. For thermostat- or humidistat-controlled equipment that is compressor-on or element-on time, usually a fraction of the hours it is switched on. The model assumes constant average power and one flat rate, so it does not represent inrush current, defrost cycles, variable-speed modulation, standby draw between cycles, or a tiered or time-of-use tariff. Zero hours or zero days returns zero cost rather than an error, and negative inputs are rejected.

Worked example

A 500 W dehumidifier that actually runs 10 hours per day uses 150 kWh over 30 days. At 18¢/kWh, that costs $27.

Second worked example

A second case shows what cycling does to the answer. A window air conditioner labeled 1,200 W does not draw 1,200 W all afternoon: on a 90 °F day a correctly sized unit might run about 60 percent of the time. Across 8 clock hours that is 4.8 hours of compressor time, so 1,200 × 4.8 ÷ 1,000 = 5.76 kWh a day. Over a 90-day cooling season at 18¢/kWh the cost is roughly $93, not the $155 that plugged-in hours would suggest.

How to read the result

Treat preset watts as a first estimate. Nameplate input and average cycling power can differ, so measured kWh over several representative days is the best refinement.

Sort the result by what it justifies. Under $2 a month the appliance is noise on a household bill. Between $2 and $15 a month a schedule, setpoint, or timer change usually pays back immediately at no cost. Above $15 a month replacement economics begin to work: a unit costing $20 a month to run that a modern equivalent would run for $10 repays a $300 purchase in about two and a half years. Above $40 a month, measure the real draw with a plug-in meter before spending anything.

Planning inputs are deliberately editable because two homes in the same state can have different tariffs, roof conditions, equipment, and operating schedules. Save a scenario with “Copy link,” then change one assumption at a time. This makes the result useful for comparing decisions without implying false precision.

Formulas and defaults are documented in our data method. The principal references for this page are:

1. U.S. Department of Energy — Estimating Appliance and Home Electronic Energy Use (2024) — Watts-to-kWh cost method.
2. EIA — Electric Power Monthly, Table 5.6.A (2024 annual) — State residential rate benchmarks.
3. EIA — Residential Energy Consumption Survey (2020, released 2023) — Household end-use context.
4. ENERGY STAR — Product finder and estimated annual energy use (2025) — Manufacturer-reported annual kWh for comparing a replacement against current equipment.

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