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?