Air conditioning units, the silent power consumers

I had plans to write about this few months ago, but have somehow failed to deliver.

I’m using a split air conditioning unit from Zibro. It’s several years old unit which was one of the highest end units back when I bought it.

I was curious how much it consumes when heating function is running during a winter. I’ve used it here and there when it was really cold. Plugged it through the watt-o-meter and I got my results. Turned it off and that’s when I got shocked…


While in OFF (standby) state, it was consuming ~90W of power. 90W for doing nothing at all, just being plugged into a wall socket. For reference, that’s almost like having a 100W incandescent bulb turned on 24/7!

At first I thought it’s something wrong with the measurements, but after doing some research, I’ve found out why it is like this. It’s not mentioned ANYWHERE in the instruction manuals and sales people never mention it when you’re buying AC unit.

Split air conditioning units consist of indoor and outdoor unit. And the outdoor unit is the culprit for this rather excessive power consumption behavior.

The outdoor unit also houses the compressor which pumps the coolant around the system and the reason for consumption is the heater within it, that keeps the liquids and particularly lubrication within compressor in a proper aggregate state. If lubrication becomes too thick due to very low temperatures, when you fire up the compressor it will wear significantly faster than with proper lubrication. And because of that, outdoor unit has its own thermostat that keeps compressor at a correct temperature at all times, keeping compressor always instantly ready for a wear-less operation.

Basic calculations

Where I live, winters often last from mid October till beginning of March. Roughly 5 months if we round it up. If unit is consuming power at the rate of 90W per hour, that’s 0,09 kW an hour. Times 24 for a full day makes it 2,16 kW a day. 5 months is roughly 150 days if we count them all as 30 days, making the total power consumption of 324 kWh for each winter season! 324 kWh of wasted power for doing NOTHING at all except being plugged into a wall socket. That’s a lot of power literally being thrown out the window.

For a better perspective, this is the equivalent power consumption to a 400+ liter, two door American style class A++ refrigerator running for a whole year!

Based on further research, power consumption depends on the age, tech level of the AC unit as well as outdoor temperatures. Certain newer high-end AC units have significantly lower power consumption to keep the compressor warm compared to my unit. But still, consuming even just 10W is 10W too much. Use watt-o-meter if you have one and do the measurements yourself. This mostly applies to countries that have winters. If you’re in a region with constant summer, I don’t think it’s even worth bothering. But for regions with winters, it can make a MASSIVE difference to the power bill and the environment.


If you do live in region where you have winters and you know you won’t need the AC unit for the entire winter, simply unplug it from the wall. If it’s not running, it won’t be harmed by the extremely low temperatures. This way you’ll eliminate the heater and save tons of power.

Warning and limitation!

If you do live in a region affected by winters and you plan on using AC unit for dehumidification or heating during the winter, you need to plug it into the wall socket at least 12 hours prior actually activating its dehumidifier/heater function. The heater should heat up the compressor in 12 hours sufficiently enough. Then it is safe to actually run the AC unit and use it as usual. The unit will work regardless, but be aware that you’ll significantly shorten its lifespan.

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