# How can I calculate the power consumption of an A/C unit?

I have an AC unit with the following specs:

``````Cooling Capacity: 1260 kcal/h, 1.47kW, 5000 Btu/h
Fan Motor Power: 0.034 kW
Current: 0.155 A
``````

My question is how much power does this unit actually consume in an hour? Does it use 1.47kW constantly?

Btw it's a York unit. Is that a good brand?

• You are asking two questions here - you might consider splitting this up into two distinct questions so that answers can be more focused. – The Evil Greebo Oct 23 '13 at 12:57

It will only draw that level of power when the compressor is running. In normal circumstances it will cycle on and off to chill the cooling element as needed; the rest of the time only the fan will be running to blow air over them.

The amount of power consumed will vary depending primarily on how hot it is and what temperature you have the AC set to.

To find out how much power it's actually using, you'll need to use a power meter of some sort. I'm partial to the Kill-a-Watt if they're available where you live.

• Understood. Thank you very much. Is there any audible signs that the compressor is on? – rabbid Oct 23 '13 at 14:33
• @rabbid if you hear something other than the fan blowing the compressor is running. If it's running an a constant fan speed mode; any time it gets louder the compressor's running. – Dan Is Fiddling By Firelight Oct 23 '13 at 14:51
• You will not be able to use a Kill-a-Watt device because most outdoor condensing units are hard-wired. You'll need to use a current transducer in the breaker box. But there are easier ways to estimate the power consumption without measuring it. – littleturtle Mar 10 '14 at 19:59
• @littleturtle true, but also probably irrelevant to the question. 5000 BTU/h is a small window mounted model intended to cool a single room that is powered with a standard wall plug, not whole house model. – Dan Is Fiddling By Firelight Mar 10 '14 at 21:00
• @DanNeely Good point! FYI, you can sometimes borrow Kill-a-Watt type devices from the library. – littleturtle Mar 11 '14 at 14:41

You do not have enough information to calculate the electrical power consumed during operation.

The three quantities listed, 1260 kcal/hr, 1.47 kW and 5000 BTU/hr, all represent the same power level, simply given in different units. They all give, as stated, the cooling capacity: the rate of heat energy removal from the cooled space.

A particular air-conditioner has a dimensionless number called the Coefficient of Performance. It is defined as the ratio of Energy Removed to Energy Consumed. This value, usually around 4 to 8, divided into your cooling capacity (preferably in kW), will give the electrical power consumption of the unit when running...

Another possibility: Turn off most of the appliances in your house, especially anything that cycles, like your refrigerator. Go to your electric meter and figure out how much power your house is using. The procedure for this varies between meters, but if you call your power company, they might be able to tell you how to do it.

Turn on your A/C, let it run for a few minutes, and again figure out how much power your house is using. Subtract one from the other to get the power consumption of your A/C.

Add together the kW from Cooling Capacity and the Fan Motor.

1.47 + .034 = 1.504 kw or 1504 w.

It appears that this is for a 220 v circuit ( 34w / .155A = 220v based on the fan rating).

So your total draw would be 1504/220 = 6.84 A.

• Thanks. Yes it is a 220V unit. What is the significance of the current draw versus the wattage? – rabbid Oct 23 '13 at 14:34
• You probably pay based on the kilowatt-hour. So running this air conditioner at full tilt for an hour would consume 1.5 kWh. The current tells you what size wires to use and the sizing of the breaker. – Chris Cudmore Oct 23 '13 at 14:43
• As mentioned by User58220, the kW value is the cooling output capacity, not input power. – littleturtle Mar 10 '14 at 19:57