When I drove my EV I had to deal with frequent fogging and attempted a bunch of different solutions (EVs and winter don't mix: the heater is usually a big resistor which burns a lot of the battery/range).
A few thoughts:
- The air to defrost doesn't have to be warm, in fact using the A/C may work as well since it removes the moisture from the air
- Coat the inside of the windshield with some anti-fog solution. It doesn't completely remove the fog but it does minimize it.