[kgermino]

> Using the heater does not affect range in a gas powered car.

It typically does (though not as much as the chiller would).

There's two costs to using the heater:

1. The electricity to power the fan comes from the engine. I'm not sure how much of an impact this actually is (depends on the power the fan needs) but there's something there.

2. The heat from the heater comes from the engine block, which cools the engine. On cold days (<15 F) this can have a huge impact on the engine's temperature and will often cool the engine well below it's most efficient operating temperature.

[bathat]

Look, electric cars are great, and I'm looking forward to the day when I can buy one, but this is BS.

First, the power the run the fan is minuscule. On the order of a few Watts. Maybe a few tens of Watts at most. It's an order of magnitude less than what is needed to run seat heaters (and those have almost no measurable effect on a Model S's range, which is why "range mode" uses seat heat in favor of air conditioning). The energy use you're talking about is enough to move the car an extra few hundred feet after a multi-hundred mile drive.

Second, every ICE has a thermostat on the radiator. It greatly reduces coolant flow to the radiator when the car is warming up, or any other time that the coolant is below optimal temperature. I spent many years in the northern (continental) United States and never encountered a situation where the coolant temperature gauge on an ICE car failed to show normal operating temperature after 10-20 minutes of warm-up time.

The cold-weather fuel economy difference in a conventional car mostly comes down to greater air density.

[dredmorbius]

More to the point: the energy-intensive aspect of heating an ICE car, the heat itself, is a waste product of the engine and needs to be removed regardless. Even in cold weather.

In an EV, heat must be generated at a very high energy expense. You can play with the mileage range estimator on Tesla's website. For the largest capacity (85 kWh) batter, heat knocks range down by about 50 miles. Depending on conditions, at 55 MPH, you're talking 350 to 300 or so with heat at 32F. A gasoline powered ICE will likely actually get slightly higher performance due to greater thermal gas expansion at low temperatures, and lower overall cooling demand: while running the cab heater doesn't consume much power, spinning the radiator fan does, and can usually be avoided in cold weather.

Source: http://www.faqs.org/faqs/autos/gasoline-faq/part3/

[grecy]

> I spent many years in the northern (continental) United States and never encountered a situation where the coolant temperature gauge on an ICE car failed to show normal operating temperature after 10-20 minutes of warm-up time.

Go further North. I have not seen the temperature gauge on my car move since about October, and I have a huge piece of cardboard blocking the entire radiator to stop air flow.

[pdonis]

I have a huge piece of cardboard blocking the entire radiator to stop air flow.

This won't make any difference unless the thermostat is open. If your temperature gauge is on "cold", you're not even close to the point where the thermostat will open if it's operating normally. Which raises the question: have you had your thermostat checked to make sure it's not stuck open?

[grecy]

> This won't make any difference unless the thermostat is open

Actually, it makes a huge difference as it stops an enormous amount of very cold air going through/around the radiator onto the engine. Everyone up here does it, else cars would not be warm enough to run properly.

> Have you had your thermostat checked to make sure it's not stuck open?

Of course. Everything works great in summer when it's ~+25C

To give you a better understanding of how cold -50C actually is, I can drive for an hour, get out and put my hand directly on the exhaust manifold of my 4-cyl East-West engine (exhaust at front for cooling) and it's only just warm to the touch.

It's cold. Very cold.

[pdonis]

-50C

Ah, that explains it. :-) I used to do cold weather testing when I worked as an automotive engineer; the coldest we ever tested at was -30 C, and there were plenty of test vehicles that didn't fully warm up at that temperature.

[MertsA]

Check your thermostat, if it's too cold it should block off the radiator completely meaning that your piece of cardboard would do nothing if it was working properly.

[bradleyjg]

Wouldn't colder air, and thus higher air density, be more efficient, not less efficient?

[rcvassallo]

No. There's a reason why racers love cold air intakes, and it's not for efficiency, it's because you get to burn more fuel and thus make more power!

The extra fuel comes automatically because modern EFI (electronic fuel injection) motors use several sensors in a feedback loop to ensure that the air:fuel ratio is 14.7:1

There is an air temp sensor and compensation that adds roughly 1% fuel for every 10F drop in temperature. Then the oxygen sensor in the exhaust system measures whether combustion is hitting the 14.7:1 target and adds or subtracts fuel accordingly.

[stcredzero]

Drag goes up proportional to the density of the fluid. Having more oxygen to run your engine will give you more energy, but I suspect that it won't keep up with increases in drag.

[pdonis]

Oxygen density is also proportional to the density of the fluid, so this should be a wash.

[bradleyjg]

Yeah I suspect this is it. The density is inversely proportional to temperature and drag is proportional to to density. Even if the engine is more efficient (in a steady state) with denser air, the relationship is probably sub-linear.

[MiguelHudnandez]

I think lower ICE fuel economy comes at higher altitudes, not necessarily colder climates -- though there is a correlation.

The sparse atmosphere robs the engine of power, just as it reduces your body's ability to gather oxygen.

[to3m]

My car is markedly less efficient in winter on short trips, even though England doesn't moves vertically with the seasons. Over longer journeys this phenomenon is much less of a problem.

The engine's preferred operating temperature is much higher than any reasonable air temperature, and until that point is reached the engine oil will be less lubricative and the fuel (particularly in the case of diesel) less inclined to combust. It will naturally take longer to reach that preferred temperature when it is cold outside, because not only is the air cold but the engine is also this big lump of cold metal, absorbing the heat of combustion and pulling it away from the cylinder where it is needed.

[nomdenom]

The sparse atmosphere robs the engine of power, but that doesn't mean that it is less efficient, I think that matters on the car/driver.

Personally, high altitude driving helps my fuel economy -- I would speculate that it's due to decreased air resistance and the lack of power forcing me to drive a little more conservatively.

[pdonis]

Colder weather reduces fuel efficiency because during warmup, extra fuel is injected into the cylinders to maintain performance, since it's harder to get ignition when the air is colder. In other words, better to waste some fuel than to hit the gas and have a lot less acceleration than usual.

[namdnay]

In a modern car, the ECU controls the air intake pressure, so all higher altitude would mean is that the turbo system would spin a bit faster.

[ken_railey]

This is reaching a bit.

1) The nominal amount of electricity used by a heater blower motor is not going to measurably affect the range of your trip (this is most likely the same for the Tesla)

2) The heat from the engine block is waste heat from the relatively inefficient combustion process. This heat has to be actively dissipated in most driving conditions (typically even in winter). It is essentially free to pipe this heat into the cabin. Now contrast this with the Tesla's 400 electrical resistance heater, which has to directly compromise range to generate cabin heat.

[DannyBee]

I'm mildly curious why they use direct electrical resistance. It's not like you can't make heat pumps that operate down past 0F.

My mitsubishi mini-split: 1. Can produce it's full BTU load all the way down to 5F, and 75% BTU load down to -13F. 2. Doesn't bother to blow air until it's warm :)

They aren't even that much larger than a resistance based coil system (though I could imagine the model S may not be able to fit them)

[pdonis]

The electricity to power the fan comes from the engine. I'm not sure how much of an impact this actually is

The fan practically never runs in cold weather. The only time it's needed is in hot weather, when you're stopped or at low speed and there's not enough airflow over the radiator and/or condenser. In cold weather the thermostat controls engine temperature, not the radiator, so the fan never gets told to turn on.

[modoc]

Not the radiator/cooling fan(s), the climate control system/vent fan(s.

[pdonis]

Ah, ok. That actually does draw a significant fraction of the available power on the 12V electrical system (in my car the interior lights dim perceptibly when the climate control blower is on high), but by the standards of the engine it's still not much.

[eli]

Isn't it using electricity that is already being generated by the alternator whether the heat is on or off?

[function_seven]

No. The greater the electrical load placed on the alternator, the greater the parasitic load on the accessory belt.

That being said the amount of electricity, and thus the load on the belt, to run the fan is very very tiny compared to the energy required to heat the air. In an ICE, the heat energy is literally free. You were going to dump it anyway, might as well be into the cabin.

[jessaustin]

I agree with siblings that we're not talking about a significant effect on mileage, but technically there is still an effect. When the ventilation fan kicks on, this will be an additional current draw. Since the voltage regulator is an analog device, it will respond to the resulting slight dip in system voltage by increasing the alternator field strength slightly. The engine will then have to apply slightly more torque to the alternator, which will burn slightly more fuel.

Since engine speeds vary greatly, having a dumb alternator that provided power scaled in proportion to RPM would be a disaster.

[MertsA]

That's not how a generator works. Take a DC motor and spin it with your hand and it'll generate a bit of a voltage potential across the terminals on the motor. If you short those together and then try to turn the motor you'll notice that it's significantly harder to turn.

[tbrownaw]

Not exactly... the alternator provides "up to" a certain amount of electricity, but as more of that electricity is actually used for things it gets harder for the engine to spin the alternator and so you end up using (slightly) more gas.

The alternator (or really any electric generator) has a magnetic field, and a lot of coiled up wire. Moving the wire thru the field generates electricity, the faster the wire moves the higher the voltage is. But the more current is moving thru the wire (more load, more things using the electricity), the more it pushes back against the magnetic field (because that current in the wire generates its own field) and so the harder it is to make it move.