I knew the EV Rav 4 used the ac in reverse as a heat pump, but didnt know they did that on the prius too. I knew it used a thermos to store 3/4 of the coolant for quicker start ups and it ran at start up to get the engine up to operating temp and also runs as needed to maintain temp along with a host of other factors.
I knew a few gen 2 prius owners who would complain of not being able to beat 43 mpg when winter came and they used the heater. I can see the heat effect mpg in my insight when it gets cold out on level surface I can crank it up and down temp wise without touching the blower speed and watch my mpg.
