Estimate your summer electric bill for a window or portable air conditioner and compare inverter AC savings.
Monthly running cost
$22 / mo
Annual monthly average (~$66/mo during active season)
Example calculationCalculated
A 1,500 watt space heater used 8 hours a day for 120 days costs about $66 a month during the active season ($22 a month averaged across the year, or $259/yr) at $0.18 per kWh.
Cost per hour
$0.27 / hr
While operating
Cost per day
$2 / day
Active + standby
Cost per year
$259 / yr
Total annual spend
Annual electricity
1,440 kWh/yr
Energy consumed
Note on electric space heaters
In winter, heat from an electric space heater directly warms your living space, reducing the workload on your central furnace or boiler. Because of this heat replacement, not all electricity spent on a space heater is extra cost.
However, electric resistance heat is far more expensive per delivered BTU than modern cold-climate heat pumps. See our Heat Pump vs Oil, Gas or Propane Calculator to see if a heat pump pays.
Efficient upgrade payback
Annual savings
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Electricity saved
Payback period
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Time to break even
Lifetime net return
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Over expected lifespan
My home appliance list
Add several appliances from the left rail to see where your electric bill is going and which devices use the largest share.
Appliance
Watts
Usage
kWh / yr
Cost / mo
Cost / yr
Bill share
Action
No appliances added yet. Click “Add to my home list” on the left.
Total
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100%
Does a bigger upgrade pay?
If high-draw appliances dominate your bill, explore our in-depth calculators:
Heat pump vs oil, propane or gas: Replace inefficient resistance space heaters or old boilers with efficient cold-climate heat pumps.
Rooftop solar: Generate your own clean electricity to offset heavy air conditioning or appliance loads.
Home battery storage: Shift electricity consumption away from expensive peak utility hours or power critical appliances during blackouts.
Electric car vs gas car: Calculate how charging an electric vehicle at home compares to buying gasoline.
How this calculation works
Appliance running costs are calculated by multiplying electrical energy consumption in kilowatt-hours (kWh) by your local utility electricity rate.
1. Calculating Kilowatt-Hours
For standard electrical appliances, energy consumption is computed from rated operating wattage, hours of operation per day, days per year, and the device's duty cycle: kWh = (Watts × Hours × Days × Duty Cycle) / 1,000. For devices with standby power (clocks, microcontrollers, transformers), standby energy is added for the remaining hours of the day: (Standby Watts × [24 - Hours] × Days) / 1,000.
For major home appliances like refrigerators and dishwashers, power draws cycle unpredictably throughout the day. For these devices, standardized annual kilowatt-hour ratings from official FTC EnergyGuide labels are used directly.
2. Upgrade Payback
When comparing an existing appliance with a more efficient replacement, annual dollar savings equal (Old Annual kWh - New Annual kWh) × Electricity Rate. The simple payback period represents the replacement purchase price divided by annual savings. Long-term net savings are projected using the shared DoesItPay financial engine, modeling standard 3% electricity rate growth over your chosen equipment horizon.
Disclaimer: A planning estimate based on your inputs and the assumptions shown. Actual costs and eligibility may differ. Energy consumption varies with usage patterns, ambient temperature, and device efficiency. Not engineering or professional advice.
Typical wattage, rental rates, and break-even math
A medium 8,000 to 10,000 BTU window or portable air conditioner draws roughly 900 to 1,200 watts when the compressor is active. Over a 90-day summer running 8 hours a day, that adds $35 to $55 per month at national average electric rates. Variable-speed inverter window units cut power draw by 25% to 35% during mild evening hours.
See how much a heat pump water heater saves on your bills and how many years it takes to pay back versus electric, gas or propane. Free, in your browser.