If you choose not to run the A/C, be sure to run it at least 3 min./mo. to recirculate the oil in the compressor to maximize it's lifespan, and those of the 'O' rings...
I recently turned my air con off around town on my 987 and the computer is telling me its gone from 25mpg to 29mpg. so its a costly item around town. my son has a 986 and he gets 29mpg with it off.I now drive with it off in all but the most nessasary conditions.