Several days ago, I pulled my new Prius IV into a touchless wash system. It was sunny and about 90 degrees outside of the car. There was a small line of cars waiting to use the car wash, so I pulled up behind the last car and put the car in Park. The engine shut down and the air conditioning continued to work flawlessly. I was in line about 20 minutes and the A/C continued to work without the engine ever starting up. I was in the Eco mode, so I guess the A/C used less power than in Normal mode. My reaction to this was WOW! My car was staying at 75 degrees in 90 degree weather and I didn't have to keep my engine running. I had plenty of reserve power in the main battery.
I've noticed that my 2010 is much more efficient while running the A/C with the engine off than my 2006. Definitely a nice feature and one that further helps achieve such high MPG's during city driving.
Similar experience here but in 106+ degrees in Goodyear AZ. The ICE would cycle on any time the battery charge got down to two bars, then would shut off w/ three bars. I would say it is an efficient system. Now the initial cool down - no solar roof system - in this heat took quite a long time, perhaps up to 10 minutes to a comfortable level.
