India, Oct. 29 -- The mornings have turned cold. You get into the car, switch on the heater and wait for the windshield to clear. In a petrol or diesel car, the engine's own heat does the job. In an EV, that warmth comes from the battery, and you can watch the range figure drop as it does.

Either way, keeping a vehicle at the right temperature, in cold or in heat, has become one of the biggest engineering challenges in the industry, whatever powers the car.

Why this is harder, than it used to be?

Think about how climate control used to work. A petrol or diesel engine produces plenty of waste heat, so warming the cabin in winter cost almost nothing. In summer, a belt-driven compressor handled the cooling. It wasn't the most efficient se...