Cooling cost comparison
Window AC vs. portable AC: which costs less to run?
Run the calculator once with the window unit and again with the portable unit. The useful comparison is the cost to keep the same room comfortable—not wattage or BTU alone.
Appliance energy cost
Use the power label on your appliance and the electricity rate shown on your bill.
Formula: watts ÷ 1,000 × hours per day × days × electricity rate. Cycling appliances and variable-speed equipment can use less than their full rated power.
What changes the answer?
Compare units sized for the same room
A smaller unit can look cheaper simply because it provides less cooling. Compare models intended for the same square footage and account for sun exposure, ceiling height and room use.
Portable units can run longer
A single-hose portable unit exhausts indoor air and can draw warm outdoor air through leaks. A window unit keeps more of the heat-producing equipment outside and may reach the set temperature sooner.
Use measured average watts when possible
Variable-speed compressors and thermostat cycling make nameplate watts an imperfect daily average. Measure each unit across a representative hot day, then enter average watts and actual operating hours.
Use this result as a planning range
Follow the installation, drainage and electrical instructions for the exact air conditioner; do not defeat window supports or use an undersized extension cord.
Review the formulas and public sources in our methodology.
Official references
- Appliances and ElectronicsU.S. Department of Energy
- Electric Meters and kilowatt-hoursU.S. Department of Energy
- How to use the EnergyGuide labelFederal Trade Commission
- Room air-conditioner buying and sizing guidanceENERGY STAR