Couldn't a heater be integrated into the glass by adding a conductive layer similar to what's used for LCDs? That combined with making the glass double pane should be able to greatly cut down on the power needed to prevent the glass from fogging up.
Yes, electrically heated windshields are standard equipment on my EV (and a lot of other higher-end EV and ICE vehciles), and it works very very quickly. I'd guess that the additional cost of the small wires embedded, adds a small amount to the total cost of the windshield, but it's a smallish number when compared to the labour and shipping costs of a windshield replacement.
Looking at the numbers that someone else posted, the ones in
Green are EV only, the ones in
red would equally apply to an EV or ICE vehicle as an ICE would have to generate the electricity. This is the kind of annoying argument that pro-ICE people throw out, and never stop to think about; Electricity & Air Con are not free on an ICE vehicle, they cost hydrocarbons to generate/operate. In fact I'd argue that the AC is likely more efficient on an EV because it's operating in a cooler environment and not surrounded by a very very hot engine mass.
Baseline (vehicle at rest but powered up): 247 Wh = .74 mph
Defroster (rear window & side mirror heaters): 285 Wh = .86 mph
Steering Wheel Heater: 95 Wh = .29 mph
Heated Wipers & Nozzles: 95Wh = .29 mph
1 Seat Heater: 57 Wh = .17 mph
2 Seat Heaters: 1cabin reached 108 F quickly33 Wh = .40 mph
3 Seat Heaters: 171 Wh = .51 mph
4 Seat Heaters: 209 Wh = .63 mph
5 Seat Heaters: 247 Wh = .74 mph
HVAC at ‘HI’ or 82F (28C): 6.4 kWh = ~18..20 mph
HVAC at 74F (23C): 342 Wh = 1.03 mph
As for total 'idle' power consumption, my car with the heater on medium, on a cool (2C) day, the front and rear defroster, headlights etc, I've never seen more than about 1.5kW (or that's what is being reported); although my heater is a heat pump, not just a coil of wire.