If you desire, you can press the physical A/C button on the drivers side of the center stack console to disable the compressor - it will show "A/C OFF" in the VFD/LED display of the climate controls...however this may not have the desired effect if what you really want is cooling.
I forgot about this one time and had a laugh as my friend on the passanger side had turned the temp dial all the way down to "LO" - I figured he must've been frozen off his chair but had forgot that I turned the "A/C OFF" earlier in the day when it was much cooler to save battery.
At any time if you press AUTO once or twice it switches the compressor back on in order to comply.
I wanted to amend my post to say I only actually turn the compressor off on cool days, from my prius days I remember that it's a good idea to try to preserve the life of the battery pack by making it as comfortable as the rest of your passengers..
Edited by jestevens, 25 June 2015 - 06:11 AM.