Originally Posted by eastsidebuzz
So I would think the larger fills quicker then the small. So the power used would be comparable or negligible.? What I don't want to do is buy a v8 when a v6 is less gas mileage. I am assuming that the 5hp is my v6 and it is the same on both compressors just the compressor piece is different and runs at different rpm's.
Just because a motor has a power rating of 5 HP does not mean it is always making that much power. Basically the rating means it has the potential to make that much power and draw a proportional amount of electricity to the power it actually makes, this is dependent on the load applied. The larger compressor would draw more power while running but that will be partially off-set by the fact the bigger slower turning pump will be more efficient and make more air per watt of power consumed. The power cost differences between these two compressors will be small and any savings would probably be with the bigger one but only over a long period, it actually would be negligible unless you are running a full time multi-duty shop.