Heating and Cooling Running Costs: Watts, Hours, and Rates
Seasonal comfort loads often dominate a household electricity estimate. This guide explains the shared worksheet method for air conditioners, heaters, and space heaters—using watts, hours, and a rate you enter—without treating the result as a provider invoice.
One identity for every device class
Daily energy in kilowatt-hours is (watts ÷ 1000) × hours used that day. Cost is kWh × your energy charge ($/kWh). Month and year figures scale that daily average by the days you set. The U.S. Department of Energy’s Energy Saver materials and EIA unit/conversion explainers use the same watts→kWh relationship; our appliance worksheets apply it to one device at a time.
Build a heating or cooling scenario
Find running watts
Use the nameplate, manual, or Energy Guide average—not locked-rotor surge for motors.
Estimate daily hours
Use a seasonal average at or below 24 hours, not a single extreme day.
Enter your rate
Paste the volumetric energy charge (or a blended average) from your bill.
Pick the matching worksheet
AC, heater, or space-heater pages share the same math with device-labeled defaults.
Heaters vs space heaters
Central or room heater worksheets and the space-heater page use identical arithmetic. Choose the page whose label matches the device you are modeling so assumptions stay clear when you compare scenarios. Cycling loads need average running watts, not peak nameplate alone.
When to step up to whole-home views
If you need several appliances on one canvas, use the appliance energy cost or home energy usage worksheets. Refrigerators, washers, and dryers follow the same kWh identity with different typical hours—open those labeled tools when the device class matters for communication, not because the formula changes.