How much electricity does an air conditioner use per hour?
Short answer
A 12,000 BTU split uses between 0.9 and 1.4 kWh per hour depending on its efficiency, but only while the compressor is working. That's the key: a conventional unit switches on and off at full power, while an inverter lowers its output once it reaches temperature and so uses considerably less over long sessions.
The air conditioner is the appliance that weighs most on the summer bill, and also the one surrounded by the most myths. The real calculation is simpler than it looks, but it has a catch: the unit doesn’t consume all the time.
Approximate consumption per hour
| Frigorías | BTU | Per hour (compressor working) |
|---|---|---|
| 2250 | 9000 | 0.7 - 1.0 kWh |
| 3000 | 12,000 | 0.9 - 1.4 kWh |
| 4500 | 18,000 | 1.4 - 2.0 kWh |
| 6000 | 24,000 | 1.9 - 2.7 kWh |
The range is wide on purpose: the unit’s efficiency changes the number quite a bit. Two 12,000 BTU units can consume very differently.
To turn it into money, find the price per kWh on your bill and multiply. That figure varies by distributor, tariff and month, so there’s no point printing one here.
The catch: it doesn’t consume every hour it’s on
This is what makes most home estimates go wrong. An air conditioner doesn’t consume constantly. It cools until it reaches the temperature you set, and there the compressor — which is what draws power — stops working at full output.
That’s why the inverter changes the maths:
- Conventional: the compressor is at 100% or off. It cools, cuts out, the temperature rises, it starts again at full power. Each start is a consumption spike.
- Inverter: starts strong and then lowers the output to hold temperature, without cutting out. Fewer spikes, steadier and lower consumption.
The difference shows over long sessions. Twenty minutes, and it barely matters. Six hours straight — real January use — and the inverter pays for itself.
18 degrees does not cool faster
It’s the most expensive and most widespread mistake. The unit always cools at the same speed; the thermostat only decides at what point it stops working.
Setting 18 degrees accelerates nothing: all it does is keep the compressor working long after the room was already comfortable. 24 degrees is where most people are fine without punishing the bill.
What lowers consumption for free
- Close the door. If it’s open to the rest of the house, the unit is cooling square metres you didn’t count.
- Lower the blind on the sunny side. The heat load through a window is enormous.
- Clean the filter. Dirty, the unit works harder to move the same air. Free, and noticeable.
- Don’t oversize it. A bigger unit than needed cycles constantly and ends up using more than a correctly sized one.
Frequently asked
How much does an inverter actually save?
It depends almost entirely on how many hours in a row you run it, and this is what few people explain well. A conventional unit always works at 100%: it cools, reaches temperature, cuts the compressor, the temperature rises, and starts again at full power. Each start is the moment of highest consumption. An inverter, by contrast, starts strong and then lowers the compressor's output to hold the temperature without cutting out. If you switch it on and off in short bursts, the difference is small. If you keep it running four, six or eight hours straight — typical summer use — the inverter can use considerably less. It's the upgrade that pays for itself fastest in an Argentine summer.
What temperature should I set it to?
Around 24 degrees is the point where most people are comfortable without punishing the bill. Every degree lower forces the compressor to work longer, and the difference between 24 and 20 degrees shows strongly in consumption. One thing that confuses many people: setting 18 degrees does NOT cool faster. The unit always cools at the same speed; all that changes is the point at which it stops working. Setting 18 to cool quickly and then forgetting about it is the most common way to double the bill for nothing.
Does switching it on and off use more than leaving it running?
On a conventional unit, the starts are the moments of highest consumption, so switching it on and off every half hour is worse than leaving it working. On an inverter the answer is clearer still: it's designed to hold temperature at low power, so switching it off and back on forces it to do the strong start again. The practical rule: if you'll be back in the room within an hour, leave it; if you're leaving for longer, switch it off.
What else affects consumption besides the unit?
Far more than people think, and it's mostly free or cheap. A room with the door open to the rest of the house forces the unit to cool square metres that weren't in the plan. Lowered blinds or closed curtains on the sunny side greatly reduce the heat load. A dirty filter makes the unit work harder to move the same air, and cleaning it is free. And a badly sized unit, especially one bigger than needed, cycles constantly and uses more than a correctly sized one.
Ready to choose?
These are the guides with real products and verified prices that match this question.
The figures in this note are based on the products' public specifications. How we do it. See all questions →
