Formula
Power is converted to kilowatts, then multiplied by time and your rate:
kWh = watts / 1000 × hours per day × days
Cost is that energy times the price per kilowatt-hour, rounded to the nearest cent. A duty cycle over a year, a meter difference, a kilowatt-hour total, and volts times amps each start from a different measurement, so they are separate pages.
Assumptions
- The appliance draws the watts you enter whenever it is on.
- The price is yours to type. No city or country tariff is built in.
- Standby time is included only if you add those hours.
Worked example
A 1,500 watt load for 4 hours a day over 30 days uses 180 kWh and costs $27.00 at $0.15 per kWh.
Input definitions
- Power
- The wattage on the appliance label.
- Price per kWh
- The energy rate from your own bill, not a national average.
Limitations
Tiered rates, time-of-use prices, taxes, and fixed monthly charges are not modeled. Solar production and battery storage are separate decisions.
Questions
Why is there no local electricity price?
Rates change by utility and season. The figure you type is the one that gets multiplied.
Does changing the currency convert the rate?
No. It only changes the symbol. Enter the price in the currency you already use.