Running cost
How much electricity does an air conditioner use? SEER and SCOP with examples
An inverter air conditioner is the cheapest electric way to heat and the only sensible way to cool, but what does it cost per month? The sum is simple once you know three numbers from the label.
5 min readUpdated
The three numbers on the label
Rated capacity (kW) is the heat moved; the power drawn is several times smaller because the unit moves heat rather than making it. SEER (cooling) and SCOP (heating) say how many times smaller, averaged over a season: SEER 7 means 7 kWh of cooling for 1 kWh of electricity.
The formula the label uses
Annual cooling consumption (kWh) = cooling capacity (kW) × 350 h ÷ SEER. Annual heating consumption = heating design capacity (kW) × 1400 h ÷ SCOP. Replace the EU reference hours with your own for a real estimate.
Example 1: bedroom, 9000 BTU, A++
A 2.5 kW unit with SEER 7.0 running 8 hours a night for 90 nights at about half load: 2.5 × 0.5 × 8 × 90 ÷ 7 = 129 kWh per season, roughly 19 € at 0.15 €/kWh.
Example 2: living room, 12000 BTU, winter heating
A 4 kW heating unit with SCOP 4.6, 10 hours a day for 150 days at 60% load: 4 × 0.6 × 10 × 150 ÷ 4.6 = 783 kWh, about 117 € for the winter. The same heat from a resistive heater would cost about 540 €.
A+ vs A+++ in money
About 35% less cooling consumption and 20–25% less heating consumption. For a daily-use room that also heats, the higher class pays back in 5–7 years; for a rarely used room it does not.
What really raises the bill
18°C instead of 24–25°C in summer (+30–40%), open windows, clogged filters (up to +15%), an outdoor unit in full sun and permanent turbo mode. Inverters are most efficient running long at low speed.
Frequently asked questions
How much does a 12000 BTU unit draw per hour?
About 1.0–1.2 kW at full power; 0.3–0.5 kWh per hour at the medium speed an inverter settles into.
Is heating with an air conditioner more expensive than gas or pellets?
With SCOP above 4 it is usually cheaper than resistive electric heating and comparable to or cheaper than pellets and gas for one or two rooms.
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