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Comment by lancesells | Hacker News Reader

The use of AC / Heat will also just burn through your battery or your gas at a much faster rate.

Slight nitpick: Using heat won't affect gas consumption of an ICE car. The heat is waste heat that otherwise would be dissipated through the radiator at the front of the car. Turning on the heat diverts coolant to a heat exchanger (tiny radiator) in the ventilation system that warms the air in the cabin.

Old trick for people that had cars with somewhat inadequate cooling systems: open the windows, turn on the heating to full helps to cool the engine.

However note that sometimes the A/C will be on at the same time as the heater in order to dry out the air.

This is one of those stupid facts that lives rent-free in my head. "If you want 'dry' hot air you need to dry it before sending it to the heater. The primary purpose of the A/C is to dry the air(this also happens to cool it), there is already an A/C unit in the ductwork, profit" But I decided to fact check myself and was not able to find much information. I did find one page that said this mainly occurs on the "defrost" setting, which makes sense as this is what is used when you don't want your windows to fog.

Regarding conditioning/drying the air instead of cooling it: the first modern air conditioners were invented primarily to dry the air, cooling was a side effect. The term "air conditioner" itself originally referred to moisture content as I understand it.

Thanks. Learned something today!

Heating for ICE vehicles is free because it redirects engine heat.

If your engine is overheating, one of the things you should do is turn the heater on max.

And since overheating usually happens on a hot day, open your windows and try to point the ac vets out them too.

Does heating in internal combustion engine cars really affect fuel consumption? My assumption was that most cabin heat was waste heat from the engine, that would otherwise be vented out? Given the dismal efficiency of ICE, shouldn't it be enough to keep a cabin warm even in quite cold climates?

The engine by itself produces a lot of waste heat. But modern engines are more efficient and take a while to warm up (especially diesels, but small turbos like Honda 1.5 too) so cars sometimes implement resistive heating to heat the cabin quicker.

Also some cars have independent heating that can be used to heat up the car up without running an engine. Not sure how exactly it works but I think it uses special battery.

AC compressor of course takes a lot of power.

Which ICE cars use resistive heating? I've never seen an alternator large enough on an ICE car to do it. (I'm also skeptical of how well that'd work on a 12v electrical system)

Hybrids will commonly have them so they can run climate control independent of the engine (at least until the HV battery gets too low) and also bring coolant temp up faster. It seems like they are usually called the PTC heater or supplemental heater.

Ford also seems to offer them as an option (e.g. as part of the cold weather package)for a number of their straight ICE vehicles like the Bronco sport, Escape, or F-150.

See this https://shops.audi.com/en_GB/web/zubehoer/p/retrofit-solutio... for example. I can only assume it's resistive, since it doesn't start the engine - but it might be a system for running the AC heatpump without engine, maybe. Also now that I think of it, window defrost is resistive.

I would guess system like this would be rare in US, because you are allowed to have remote start on your cars.

edit: never mind, it burns fuel https://www.auditech.org/acont-1427.html

Electric window defrosters are really low wattage - because its just trying to raise the temperature of the surface of the glass by a few degrees. Generally IIRC no more than 25-30a - which is a fair bit on a car with a 100a alternator - but less than for example the blower for the air conditioner.

I never thought I'd see the return of the gasoline heater. I wonder if its offered in the states.

Block heaters can be used to heat the engine coolant (and afterwards the cabin) with or without running the engine. I doubt any cars have special batteries for these (even a drive battery of a non-plugin hybrid is somewhat small to be useful); block heaters that don't require external electricity simply use the car's fuel in an auxiliary burner.

The heat pump in the Tesla Model Y definitely uses electricity, but it is somewhat efficient. Much much more efficient than early model Nissan Leafs for a night and day comparison.

Heat generally won't, in a modern ICE, that will capture a lot of the engine heat, though there are still electric and auxiliary heaters.

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