LBV, what's your opinion on the heating system? I see lacklustre heating as a common gripe especially in the extreme cold weather, but I'm keeping in mind that a lot of the complaints might be a result of people that aren't taking advantage of preheating, or are not operating the HVAC system properly perhaps.
mxs hits the nail on the head with his comment. Depending on how much range the car gets (& your personal preference between battery depletion & comfort), during the cold months you literally do need to choose between EV range and cabin heat. Or a mix of the 2.
But to answer your question, the heating system is fine. There are 3 modes for heating: FAN, ECO, & COMFORT with the % of battery assigned to climate control use increasing from 3% on Low FAN to 100% on High COMFORT. When I do use the cabin heat, I'll typically start on COMFORT to get the inside heated quickly and then switch to ECO. I'll sometimes then switch to FAN if I'm 5-10 minutes away from my destination as the coolant is warm at that stage and will retain some heat until it cools down, at which point I'm turning the car off anyway. Keep in mind that FAN will NOT keep the coolant warm (like the other 2 modes) so you're saving a bit of range.
Regarding the preheating you've alluded to a few times, that's something you ideally do when plugged into 240.
Here's my routine ... I get home from work, park in the garage, and plug the 240 in. I've got the settings in the car configured to commence charging at 7 pm when Hydro rates go down. It's fully charged from zero km in 3 hrs 40 mins but the car stays plugged in all night. About 10 mins before I'm ready to leave for work the next morning I take the 2nd remote I have in the house and remote start the car. It's plugged in so the gas engine will NOT start so no worries about CO poisoning. The car, being electric, doesn't really remote "start" as a gas engine car does. It just heats up the cabin in COMFORT mode. Because I'm plugged into a 240 circuit the drain on the heating does not drain the battery at all (120 it would). I get into the car and it's toasty warm.
At this stage I can put the heating mode into ECO and maintain that heat as I drive off. But I put it on FAN only ... which will only gives me heat for 5-10 minutes as I alluded to above.
If my ERDTT is set to -10 the gas engine kicks in every 5 min's or so and provides "free" heat so the FAN will suffice to keep the cabin warm. If it's warmer than -10, I prefer to eek out the EV range so I, like those Northerners, rock heated glove liners and heated insoles ... had them from riding the Guzzi in cooler weather anyway so why not. I should also say that my commute back & forth and lunch errands are about 55 km so that's why I do that (ie. I'm right on the edge of the cold weather range). If it was less, I'd use the ECO mode more.
It's all a personal preference but I think we owners tend to eek out the most range as it get's into your psyche strangely enough to try and get home without using the gas engine ... and plus the car does drive so much better on battery alone. The gas engine works as a generator to power up the battery (not the wheels) so there's a disconnect when the engine is revving away yet you're only going 10 km up a steep hill.
So as you can see, there are a lot of variables if you choose to use them in the pursuit of maximum efficiency. I doubt your wife will care about all of that and the beauty of it is she doesn't need to care ... just put it into Drive and use the heater like any other car and the engineers took care of the rest.
Tell me more about where your Volt would be parked and I'll expand a bit more ...