Air conditioner energy consumption calculator
Cooling capacity and electricity used are not the same thing.
Your inputs
Your inputs are processed on your device and are not sent to a server.
Example loaded. You can change any value.
There is no figure yet: nothing is calculated until you ask for it.
- Enter your measurements.
- Check the units and the assumptions.
- Press Calculate, or load the example.
Rather see a worked case? Press “Load example” and change any value afterwards.
Next step
Consumption in watts only makes sense once you turn it into money.
Where each number comes from Conversion constants are exact; densities and coverage rates come from cited sources; everything else is an assumption you can change. Methodology · Sources and updates
How to use it
- Choose whether you know the electrical power or the capacity and efficiency.
- If you have the rating plate, use the input power: it is the most reliable.
- Set the hours of use per day and days per month.
- The result gives kWh per hour, day, month and season.
How it is calculated
Consumption is worked out from the electrical power, never from the cooling capacity:
This is where most of the bad information circulates. A 12,000 BTU/h unit does not consume 12,000 W: BTU/h measures the heat it removes from the room, not the electricity going in. A 12,000 BTU/h unit with an EER of 10 draws 1,200 W.
If you use a seasonal figure (SEER), remember it averages a whole season including starts, stops and part load. It is right for estimating a summer's bill, not the consumption of one specific hour.
Worked example
A unit drawing 1,000 W, 8 hours a day, 30 days:
- Per hour: 1 kWh
- Per day: 1 x 8 = 8 kWh
- Per month: 8 x 30 = 240 kWh
- Per season (3 months): 720 kWh
Using the efficiency method: a 12,000 BTU/h unit with EER 10 draws 12,000 / 10 = 1,200 W, which is 20 % more than the example above.
Good to know
- Capacity is not consumption. The BTU/h, frigories or kW on a label measure the heat the unit removes from the room, not the electricity it uses. For that you need the efficiency rating or the rated input power.
- Inverters modulate. Once the room is at temperature, an inverter unit runs at part load and draws a fraction of its rated power. Real consumption is usually lower than this calculation for continuous use.
- Starts cost. Constantly switching on and off uses more than holding a steady temperature.
- The rating plate is the reliable figure. Rated input power is printed on the unit and in the data sheet.
Frequently asked questions
How much electricity does an air conditioner use?
It depends on its electrical power, not its BTU rating. A typical 12,000 BTU/h domestic unit with an EER of 10 draws about 1,200 W, or 1.2 kWh for every hour of continuous running.
Does a 12,000 BTU unit use 12,000 W?
No, not at all. BTU/h measures cooling capacity, not electricity consumption. With an EER of 10, that unit draws around 1,200 W.
How many kWh per month?
At 1,000 W, 8 hours a day for 30 days, about 240 kWh a month. With an inverter under real conditions it is usually considerably less.
Should I use EER or SEER?
EER for consumption at full load. SEER for estimating a whole season's use, because it already includes part-load behaviour.
Is it cheaper to leave it running all day?
It depends on the unit and the insulation. An inverter in a well-insulated home can use less holding temperature than starting from hot several times a day.
Where do I find my unit's electrical power?
On the rating plate of the outdoor unit or in the data sheet, usually listed as power input or rated consumption, in W or kW.