A/C Usage and Impact on FE

[trollbait]

{Bottom line is the more efficient cars become the much greater the cost of running the AC. It's more exponential than linear and if we ever build mega mileage cars we will also have to address the gross inefficiency of conventional AC systems, even with the best modern designs of compressor.}

I believe this only applies to traditional belt driven ACs. The Prius uses a variable speed electric compressor. It doesn't directly suck off energy going from the engine to the wheels. There will be a mpg penalty of some type, since the energy it takes from the battery has to be replenished in someway, but then the battery is cooled by the cabin air. So AC use may keep it at a more efficient point.

I've heard BMW was experimenting with regenerative braking on non-hybrid cars to run accessories. With the regen brakes and a beefy battery, it may be possible to replace all the belt driven add-ons with electric.