2004- Prii employ electric air conditioning; true. This system is high voltage which means it runs off the HV circuit on the vehicle, which includes the battery, buck/boost converter and motor generators.
The auto climate control system is just like a home thermostat. You set the temp you want and the vehicle works toward keeping the cabin at that set point. It does this by managing outside air, inside air, heater core and air conditioning compressor. This fall I have moved my A/C down to a set point of 70 degrees. This summer I had it at about 74 degrees. This means that in the morning the vehicle is heating the cabin and in the afternoon when driving home it is cooling the cabin.
The efficiency of the a/c system is a combination of many factors. Automated use of recirculated air. Recirculation of air in the footwell, but not the air sent to dash vents. Combining outside and inside air in ways that maintain more inside temperature without making the cabin stale, and so forth. But the compressor also is variable speed, thus allowing the auto climate system to run the compressor at a more efficient lower speed if the cabin is close to the set point or the vehicle is working to maintain the set point.
Because the air conditioning compressor runs off electricity, it will run at stop lights or when idle when the ICE is not running. The battery is like a buffer. Since the car generates a good deal of electricity through regenerative braking, and since at cruise the engine is usually turning MG1 and generating power, the HV battery is not heavily affected by the use of A/C Most people say they only loose a couple miles to the gallon when it is very hot out and they use the A/C the most.
You really don't have much control over ICE startup. If the state of charge on the battery is such that the system wants to top off the battery the ICE will run. But the ICE will also run when it would usually not during the winter to provide heat to the cabin.
