Comments on: How much electricity is my AC unit using when it's on "fan"?

Question: How much electricity is my AC unit using when it's on "fan"?

amro — Sun, 28 Sep 2008 09:58:01 -0800

Does my window air conditioner use just as much electricity on the "fan" setting as it does on the "cool" setting?

On cooler days this time of year, I often turn my window AC unit to the "fan" setting to pull in some of that cool air from outside. I have always assumed that if the unit is functioning as a fan, it's not using nearly as much electricity as when I've got it set to "cool." Is that an incorrect assumption? And if it does use less power than when it is cooling, how much less? Is it a negligible difference or is it substantial? Would it be better to just stick a box fan in a window?

By: cabingirl

cabingirl — Sun, 28 Sep 2008 10:08:49 -0800

You're using less power because the compressor is not kicking on, which is what uses most of the power. This page claims the fan motor only consumes 10% of the total power used by the unit, but no idea where that figure came from.

By: crapmatic

crapmatic — Sun, 28 Sep 2008 10:11:56 -0800

I actually measured a window unit with a wattmeter. I can't recall specific numbers but it drew about 150W when just the fan was running, and about 1000W when the compressor kicked in.

By: drmarcj

drmarcj — Sun, 28 Sep 2008 10:49:05 -0800

Note however that even though the compressor uses much more power than the fan used to circulate air, the compressor itself only runs intermittently. So "how much more power" is a bit up for grabs - it depends on how cool it's set to, where cooler settings lead to the compressor running more.

By: ihadapony

ihadapony — Sun, 28 Sep 2008 10:58:09 -0800

What they said. Also if your goal is to get outside air inside, the window fan is a much better bet. My window AC unit just recirculates indoor air. If yours does bring in some outside air, its probably not more then 20% or so.

By: smackfu

smackfu — Sun, 28 Sep 2008 11:14:59 -0800

Keep in mind that box fans can use quite a bit of power, and are often not very efficient on the lower speeds. For instance, mine uses 75 watts on a very slow Low and 150 watts on a very good High. It's like leaving an extra incandescent light bulb on for hours at a time.

If you're really interested in this, a Kill-o-watt meter is a great investment.

By: thinkingwoman

thinkingwoman — Sun, 28 Sep 2008 15:06:59 -0800

i used a kill-a-watt to find this out...you use about seven times as much energy using the compressor as just the fan.

By: amro

amro — Mon, 29 Sep 2008 10:36:27 -0800

All of your answers were helpful, so I have marked them all "best."