Home & DIY
How much does it cost to run an air conditioner?
Monthly kWh and bill for your air conditioner (from room size or BTU) plus fridge, washer, TV and other appliances — with summer total.
Quick answer
The sticker shock of summer cooling is rarely the purchase price — it’s the electricity bill. A 20 m² bedroom typically needs a 12,000 BTU unit; a modern inverter (SEER ~7) draws about 500 W when the compressor is running. Formula: monthly kWh ≈ (BTU ÷ (SEER × 3.412)) × hours/day × days × 0.65 duty cycle. Worked example: 12,000 BTU, SEER 7, 8 h/day for 30 days → ~78 kWh — about €19/month at €0.25/kWh, or ~€57 for three summer months.
Air conditioner
AC cost per month
$0.01
- AC electricity per month
- 0 kWh
- AC cost (3 summer months)
- $0.04
Other appliances (optional)
Total monthly cost
9.99
- Total electricity
- 133 kWh
- Other appliances per month
- 133 kWh
- Other appliances cost
- 9.98
Not sure about BTU? Room size → BTU calculator
AC cost uses watts ≈ BTU ÷ (SEER × 3.412) with the compressor running ~65% of the time the unit is on — real bills also depend on thermostat, insulation and outdoor temperature. Size the unit first with our BTU calculator on the same site. Appliance figures are average power × daily hours; fridges and freezers already include cycling. Compare inverter models before buying — a SEER 7 unit can cost 40% less to run than an old SEER 3.5 at the same comfort.
How it works
The same math extends to everything else on your bill: kWh = watts ÷ 1,000 × hours per day × days. A fridge at 150 W average runs ~108 kWh/month; a TV at 120 W for 4 hours adds ~14 kWh. Two levers matter before you buy hardware: efficiency class (SEER 7 vs an old SEER 3.5 can halve AC running cost) and usage (26-27 °C instead of 22 °C routinely cuts consumption 20-30%). If you still need the right BTU size, start with our air conditioner BTU calculator — this tool answers what that unit costs to keep on.
Measure before you argue with the bill: a smart plug energy monitor on the AC (or fridge) shows real kWh for a week; a smart ac controller wifi schedules setbacks so the compressor is not on while you are out. Upgrading a tired portable? Compare a proper inverter air conditioner 12000 btu split against sealing the hose with a portable ac window seal kit — the seal is cheap insurance if you keep the portable another season.
There is a second lever that changes the bill without changing a single kilowatt-hour: when you use them. Many contracts price electricity in time bands, and the same wash costs meaningfully less at night or at the weekend than at seven in the evening. Nothing about the appliance changes — only the clock. Check which tariff you are actually on before optimising anything else, because the machines that lend themselves to shifting (washer, dishwasher, water heater, EV) are exactly the ones with the biggest single-cycle draw.
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Frequently asked questions
How much does it cost to run AC 8 hours a day?+
A 12,000 BTU inverter (SEER 7) in a typical bedroom: roughly 2.5-3 kWh per day of use, or €0.60-0.75 at €0.25/kWh — about €18-22/month if you run it every day. An older SEER 3.5 unit on the same schedule can double that. Set 26-27 °C, close doors, and shade sunny windows: those three habits often matter more than the brand on the box.
How do you calculate kWh for any appliance?+
kWh = (watts ÷ 1,000) × hours used per day × days in the period. A 2,000 W oven for 1 hour a day is 2 kWh/day, or 60 kWh/month. Fridges and freezers cycle on and off — use the average power on the energy label (often 100-200 W), not the peak. Multiply the monthly kWh by your tariff to get the cost. A plug-in energy monitor removes the guesswork for mystery appliances.
Does a portable AC cost more to run than a split?+
Usually yes — often 30-50% more kWh for the same room, because the exhaust hose leaks heat back in and effective SEER is lower than rated. If you already own a portable, run it with the shortest possible hose and seal the window gap. For daily summer use, a fixed split pays back in electricity within a few seasons.
What electricity price should I use?+
Your all-in rate per kWh from the last bill — not just the energy component, but network charges and taxes if your supplier shows a single figure. In Italy many households pay €0.22-0.30/kWh in 2025-2026; in the US, $0.12-0.18 is common. Night or off-peak tariffs lower AC cost if you can shift usage, but most cooling happens in afternoon peak hours.
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