Estimate how much it costs to run an appliance based on wattage, usage time, and electricity rate.
Convert appliance wattage and daily usage hours into kilowatt-hours (kWh) — the unit your utility actually bills — then multiply by your rate per kWh. Formula: kWh/day = Watts × Hours ÷ 1000.
This works for any device with a listed wattage: check the appliance label, its manual, or a plug-in power meter for an accurate reading rather than guessing.
Standby power (devices left plugged in but 'off') is often overlooked in this kind of estimate — many electronics still draw a few watts continuously, which adds up over a full year even though it feels negligible day to day.
A 100W device run 5 hours a day at $0.15/kWh costs $0.075/day, $2.25/month, and $27.38/year.
Check a recent utility bill — it's usually listed as a per-kWh rate, sometimes with time-of-use variations (peak vs. off-peak pricing).
Yes — just use the appliance's running wattage, though large motors like AC compressors also draw a brief higher surge on startup that this simple estimate doesn't capture.
Multiple devices, standby draw, seasonal usage changes, and tiered or time-of-use utility rates all add variables beyond a single-appliance estimate.