[Bob's944]

I'd say a/c drains more like 10-15 hp if it's in good working order, and that is only when the compressor is working. The compressor part prolly weighs about 25# or so, i recently rebuilt my a/c clutch when it was on the car, didn't take the compressor out of the slot, but it should weigh close to that. Add about another 15# in hoses and such, about 10# for the condensor. (all guesses)

Yes, you definately feel the loss of power in a NA with the A/C on when driving around town. At highway speeds that changes alittle depending on if your windows are open or not with the A/C off. I would say that the added wind resistance at highway speeds with windows open and A/C off is higher than the power robbing the A/C compressor does to the engine and driving more aerodynamically clean with the windows closed. And the other benefit is it's much quieter at highway speeds with the windows closed.