I don't own a plug-in, but I'm curious: If you turn the heater on while in EV mode, does the gas engine have to start? Is there an electric cabin heater?
True, but it's not that horrible as it sounds: 1. The engine (ICE) heats up ridiculously quick then it shuts back off. 2. The amount of fuel burned is little. Furthermore, nothing gets wasted: the kinetic energy of ICE is used for additional locomotion and/or battery charging. 3. The front seats are heated, so you can opt to heat yourself alone, instead of entire cabin.
Also, additional heat is captured from hot exhaust once the engine is at running temperature. As Rozi points out, the seat heaters are an option and the high setting goes a long way toward providing comfort.
Don't seem to affect it much at all, not enough to have a clear idea of it. The main problem is demisting the windscreen; if the PiP had that electrically heated like my old Ford did, I'd be very happy to do without the heat a lot of the time.
Cabin heat is provided by engine coolant, just like traditional cars. However, once that coolant is warmed, the engine will shut off and stay off until it drops below a minimum temperature. In the meantime, you'll be able to drive along in EV without disruption to the heat being provided by the heater.
Each seat heater (driver/pass) has a 10A fuse.. so probably somewhere in the neighborhood of 100 watts per side.. so it'd be hardly noticeable
The seat heaters do not detract from EV range any noticeable amount, and they are the fastest, hottest seat heaters I've experienced.
On very cold days, for a quick run to a local store, I used the seat heater, for a long run, I turned the HVAC on.
The ICE warms up the engine coolant very quickly by routing it through the exhaust system (similar to some airplanes). We had a few days of -20C weather here shortly after I bought my PiP, and I was amazed that the heat began coming out of the vents after only about 3 minutes of running time.