This is something that I’ve been wondering about ever since I got to India a week ago, where, as you might imagine, it’s very hot…
I find that if I put the fan on, I can run the A/C at a lower power level and still feel cool enough to sleep comfortably. Without the fan, I need to turn the A/C up higher. I read somewhere that A/C uses about 10 times as much electricity as a fan. I’m not sure if this is true or not, but if it is even close to true then being able to turn the A/C down a few notches by running the fan should save energy overall. However, I also wonder if the “setting” of the A/C does not necessarily reveal everything about how much energy it is using. For example, if you had a stove on in the room, would the A/C end up working much harder and using more energy even if it was set at the same number? In other words, does that number on the dial represent a certain level of energy draw or a certain temperature? If it represents a certain temperature, then it is possible that running it with the fan-- even at a lower setting (i.e., higher room temp)–could use more energy since the fan itself heats the air in the room through friction, and this heat would have to be dissipated by the A/C. (However, even if this is true, the fan + A/C combo could still potentially save energy if the fan’s heating of the room air is basically negligible.) If the number on the dial represents a given energy draw level, then it also appears that running the fan at the same time and turning down the A/C would save energy overall. Any thermodynamics/HVAC experts out there care to opine on my conundrum? Thanks!
The dial on an air conditioner is a thermostat. It works by temperature. When the temperature of the air near the sensor (typically in the air intake of conditioner itself) is above the set point, the AC kicks in. When it hits the set point, the AC turns off. Energy consumption is a result of this process but not part of the control itself.
Friction heating of the air by the fan is not a factor. It is infinitesimal. Bottom line, running the fan consumes less energy than running the cooling unit. If you’re able to set the thermostat at a higher setting by using the fan, you’re saving energy.
the fan is probably moving cool air from the floor back up where it can fall again and doing the usual fan thing of moving air, in still air we have a sort of thermal layer around us that is warmer than the surrounding air (well unless its really hot but you get the point) by breaking this layer we feel cooler.