How to use the inputs
Select a preset for a typical example wattage, then edit the watts if your appliance label says something different. Enter how many hours per day it runs and how many days per week it is used.
Formula
Electricity is billed in kilowatt-hours. A 1,000 watt device running for one hour uses 1 kWh.
Cost = energy consumption x electricity rate
Worked example
A 1,500 watt space heater used 4 hours per day every day uses 6 kWh per day. At $0.16 per kWh, that is about $0.96 per day, $29.20 per average month, or $350.40 per year.
Assumptions and limits
- Presets are typical example wattages and remain editable.
- Average monthly cost uses annualized usage divided by 12.
- Appliances with compressors, heaters, or cycles may not draw full wattage continuously.
- Utility bills may include fees, taxes, tiered rates, or demand charges not included here.
Planning guidance
For the best estimate, use measured wattage from a plug-in power meter or manufacturer energy guide. For AC systems and refrigerators, estimate runtime carefully because cycling usually matters more than nameplate wattage alone.
FAQs
Where do I find appliance wattage?
Check the appliance label, manual, power adapter, or manufacturer specifications. If amps and volts are listed, watts are approximately amps times volts.
Why can refrigerator and AC costs differ from the estimate?
Compressors cycle on and off. The calculator estimates cost from the wattage and runtime you enter, so duty cycle and thermostat behavior can change actual use.
What does average monthly cost mean?
Monthly use is annualized from the days-per-week schedule and divided by 12, so it represents an average month rather than one exact 30-day billing period.