Formula
Watts become kilowatts, then a full year is scaled by the duty cycle:
annual kWh = watts / 1000 × hours per day × 365 × duty / 100
The electricity cost page prices a stretch of days you choose. This page answers a year, and it stops at energy.
Assumptions
- The year has 365 days.
- The nameplate watts are the draw while the appliance is on.
- The duty cycle is the share of the entered hours that are actually on.
Worked example
A 100 watt load for 8 hours a day at a 50% duty cycle uses 146 kWh in a year.
Input definitions
- Duty cycle
- The percent of the daily hours during which the appliance draws its nameplate watts.
- Nameplate power
- The wattage printed on the appliance, not a measured average.
Limitations
This is a planning estimate. The rate, sun hours, and losses are numbers you type. It is not a utility bill, a solar design, or a room-by-room load calculation.
Questions
Why is there no price on this page?
The question is annual kilowatt-hours. The kilowatt-hour cost page multiplies energy you already know by a rate.
What is a 50% duty cycle?
The appliance is drawing power for half of the hours you entered. A fridge compressor is a typical case.