Question about air conditioning

Hi all!

I sometime read that when A/C is on, it reduces by a certain percentage (5%?, 10%?) the HP of the engine. Is that true, or significant, only when the A/C is on the cold position? I ask this question because, as you know, A\C come on by default when we start our car and I usually let it in that position all year long. If A/C also reduce the power of the engine even when on the hot position (usual position during winter) it could be a good idea to put it to off during winter to save gas and power. What do you think about this?

Regards!
Claude

I do not know the percentage of HP but it certainly takes some power from the engine when you turn on the AC. Temperature setting is probably irrelevant at least on the Micra. If the AC is on then the compressor will run.

It's significant enough for me to notice. My micra is an automatic and I can tell immediately the car is not as zippy with the AC on. I only turn on my AC when it's too hot or if I need to defog the interior when it's cold/humid.

Quote:

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Originally Posted by Claude

Hi all!

I sometime read that when A/C is on, it reduces by a certain percentage (5%?, 10%?) the HP of the engine. Is that true, or significant, only when the A/C is on the cold position? I ask this question because, as you know, A\C come on by default when we start our car and I usually let it in that position all year long. If A/C also reduce the power of the engine even when on the hot position (usual position during winter) it could be a good idea to put it to off during winter to save gas and power. What do you think about this?

Regards!
Claude

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That is very true, in fact in my manual I found the following guidelines from Nissan:

"Below 64 km/h (40 mph), it is more efficient to open windows to cool the vehicle due to reduced engine load.

Above 64 km/h (40 mph), it is more efficient to use A/C to cool the vehicle due to increased aerodynamic drag."


It's significant enough that it's mentioned by Nissan, so it must be worth mentioning... no idea about a % though.

Someone with more refrigeration experience would be a better person to comment, but I would suspect the energy consumption would be similar, as the dehumidifying effect is a by product of the same cooling effect with the refrigeration? Maybe the compressor isn't needed as much for defrosting vs. actually cooling? :confused:

Claude : The only time that my AC comes on automatically is when the switch is pointed at Defrost. It can be switched off by pushing the lighted AC button or turning the switch to the straight up position or further counter clockwise.