How much does it cost to run an air conditioner per hour?

Multiply the unit's rated power in kilowatts by your electricity rate. A 1 kW portable air conditioner on a 24.5p/kWh UK tariff costs about 24.5p per hour; on a 16¢/kWh US tariff, about 16¢ per hour.

Are portable air conditioners expensive to run?

Portable units are the least efficient type, typically drawing 1–1.8 kW for 9,000–14,000 BTU of cooling, so they cost more per hour than a window or mini-split unit of the same cooling power.

What is EER and why does it matter for running cost?

EER (Energy Efficiency Ratio) is cooling output in BTU/hr divided by power input in watts. A higher EER means more cooling per watt, so a lower running cost for the same BTU.

How Much Does It Cost to Run an Air Conditioner?

Published: May 23, 2026

The price on the box tells you what an air conditioner costs to buy. It tells you nothing about what it costs to run — and over a hot summer, running cost is often the bigger number. That is why CoolingMetrics ranks every unit by cost per hour to run, not just sticker price.

The simple formula

Cost per hour = rated power (kW) × your electricity rate (per kWh)

A unit’s rated power is how many watts it draws while cooling. Divide watts by 1,000 to get kilowatts, then multiply by your electricity price.

A 1,000 W (1 kW) unit at the UK average of 24.5p/kWh costs 24.5p per hour.
The same unit in the US at 16¢/kWh costs 16¢ per hour.

Run it 8 hours a day for a 90-day summer and that 1 kW unit costs roughly £176 in the UK or $115 in the US.

When the wattage isn’t listed

Many listings quote cooling capacity in BTU but not power draw in watts. You can estimate the watts from the efficiency rating:

Watts ≈ BTU ÷ EER

EER (Energy Efficiency Ratio) is BTU of cooling per watt of electricity. Typical values: portable units around 8.5, window units around 10.5, and mini-splits 12 or higher (often shown as SEER). So a 12,000 BTU portable at EER 8.5 draws about 1,400 W. Where a manufacturer figure is missing, CoolingMetrics estimates the watts this way and flags the result as an estimate.

Typical running costs by type

For the same cooling power, efficiency — and therefore running cost — improves as you move from portable to window to mini-split:

Portable — most convenient, least efficient. Highest cost per hour.
Window — more efficient than portable, popular in the US.
Split / mini-split — the most efficient, best for a fixed install you’ll run for years.

How to cut your running cost

Buy the right BTU for the room — an oversized unit wastes energy. (See our BTU sizing guide.)
Prefer a higher EER/SEER rating for the same BTU.
Consider a mini-split if you’ll cool the same room every summer.
Use a timer and sleep mode so it isn’t running when you don’t need it.

Ready to compare? See every unit ranked by cost to run.