Seems like electric heaters would drain a lot of electricity. Never thought about this before today.
Poorly, which is one of the reasons they don’t sell well in very cold states. My Plug-in hybrid (not quite the same thing) gets much, much worse gas mileage in the winter (like 75 MPG worse) even when driven entirely within electric range, because it brings the gas engine on to heat the car. They don’t even try to heat it electrically. On all-electrics, I understand you can lose more than a third of your range when it needs significant heating.
Could you preheat the interior for a few minutes while it is still plugged in? If so, that would help reduce the drain on the batteries.
Electric cars have to cope with a lot of waste heat whilst operating, and typically have coolant loops run through the batteries. There is a lot of heat available for heating when the car is running. Not much different to an ICE. But pre-conditioning the car temperature happens when there isn’t waste heat. That will depend upon the car. The aircon is a heat pump, and can be configured to heat just as well as cool the interior, so you should expect reasonable (ie better than a simple resistive heater) efficiency until it gets really cold outside.
The reason for worse mileage in the cold is dominated by the battery chemistry not working so well at lower temperatures, and intrinsically not being able to hold as large a useful charge as at normal working temperatures. Really hot climates challenge the system as well, but cold seems to be the bigger problem.
This applies to my Tesla Model 3. I wouldn’t say it is heated “poorly,” but rather “at a cost to range.” The heat comes on sooner than from a gas car, because there’s basically just an electric space heater up front. No need to warm an engine and coolant before the heat starts flowing. Of course in a gas car, heat is a free byproduct. One of the main reasons I wanted the Model was to have a car with enough range that I can run the heat (or AC) and not have to worry about any range problems.
The heater is completely capable of blowing hot air and keeping the interior warm and the windows clear. As mentioned though, that comes at a cost to range. Preheating when plugged in helps a great deal. I can start the car heating 10 minutes or so before I want to leave, while it’s in a closed garage. Even when heating completely using battery power, it is still costs much less per mile than a gas car. The worst MPGe (whatever that is worth) I’ve seen is 65, but it’s usually 80+ in the cold and 100+ in milder temperatures.
On a dry morning with the temperature around 25F, I can preheat the car to 66 or so, and be completely comfortable only using the seat heaters and a jacket for the 15 miles to work, and not sacrifice any range. When it is wet I’ll often have to crank the heater to clear the windshield, even if I’m comfortable, just like in a gas car.
I have a BMW i3. The main battery runs the motor and air conditioning. There is a separate regular car battery to run the climate control, lights, ICE, etc. When plugged in both batteries get charged. If the need arises the main battery can charge the small one at a cost to range.
I’ll have to question both statements there.
Here is EV market share by state (i.e. percentage of cars sold that are electric). There are some northern states in the top 10 (Oregon, Colorado, Massachusetts, Maryland, Virginia), and many southern states in the bottom 10. Also, 45% of new cars sold in Norway are electric.
Yes, using the heater does use the battery and reduce range. That’s just something you need to take that into account when choosing a car. If you need to be able to drive 100 miles in a day, you should (and can) buy an electric car with >200 mile range. If you need to drive 200 miles a day and there’s no fast charge station you can stop at, you should buy a plug-in hybrid instead.
Mine (Chevy Volt) does the same on the default setting, but the engine-assisted heating feature can be turned down so it only does it on extremely cold days (can’t remember the threshold, but I’m pretty sure it’s below 20F). And of course, purely electric vehicles have more powerful heaters because they don’t have any engine to fall back on.
In addition to pre-heating, using heated seats definitely help.
To echo the cold weather message - Boston is fairly well littered with Teslas, Bolts, Volts, and other plug-in electrics. They sell just fine up here, and while I’m sure range is impacted for most of these drivers it’s still more than adequate.
(Emphasis added).
Well, mostly. The 12v battery runs the electronics for the climate control—basically, it runs the thermostat. But this article suggests that the i3’s cabin is warmed with waste heat from the batteries. The 12v system doesn’t store nearly enough energy to heat the cabin directly. So the 360-volt main battery does the heavy lifting (motion and heat pump/AC) while the 12v battery handles the electronics.
I’m posting this not to correct you, kferr, but rather to point out that this is exactly the situation Francis Vaughan describes in his post.
It’s my understanding Nissan Leaf used resistive (electrical) heating for years, but has recently switched to using its AC compressor as a heat pump, which is inherently more efficient in most situations.
I find that heating works much better in an electric car than in a gas car. You can turn on the heat before you start driving. The heat comes on immediately, without waiting for the engine to warm up. I especially like the “keep heating on” while parked (e.g. while going out shopping), feels great to come back finding the car warm, dry, clean and ready to go.
Youtuber Bjørn Nyland once slept in his electric car in the middle of Norwegian winter at minus 31C (minus 23F). The heater kept the car nice and warm all night. I don’t think you can do that with a gas car even with Webasto heater, you’d run the risk of carbon monoxide poisoning.
I’ll echo what echo says.
Practical real-world experience…
At -20C (-5F) and that temperature range, in really bad stop and go traffic averaging about 20kph (12mph), my Model 3 loses about 3km for each 1km driven. On the expressway, about 2-to-1. Since I have 500km range (actually 400km, since good battery care says don’t charge above 80% to 90% unless you are planning a long trip) it still doesn’t matter. It’s a rare day that I burn off 200km of my 400km range. It might be a bit more “iffy” if I had the shorter range 300km Model 3 allegedly coming soon.
Heat uses power based on time, while travel uses power based on distance. The slower you go, the worse this ratio. Once the interior is warmed up, you use less to heat, so the further you go, the less that you use per km to heat. I’m told the 3 has a 7kW heater. Plus, you have seat heat, so interior air temps don’t need to be the 23C (75F) I set mine to, if I were worried about range.
At about -12C (12F) the ratio is about 2-to-1. Note that these are extremes for most of the auto market at the worst time of the year. I figure it has cost me about $140 for 3300km so far, or about 4.3 cents/km; whereas my BMW in this weather goes about 400km on 60L which even at the absurdly low price of $C1 per litre is still about 15 cents a km. (BMW use premium which runs around $C1.15 to $C1.30)
So yes, colder weather uses a lot of power; but then, my BMW would get 400km to a tank in cold weather, and sometimes up to 600km in summer (about 60L tank).
OTOH, those numbers would probably be different in a land of cheap gas and expensive electricity, but that land also does not have these weather extremes for extended periods.
:dubious:
There is some waste heat available from the battery compartment, but it can’t be much. Highway cruising (75 MPH) for a sedan like the Tesla Model S probably requires about 30 horsepower at the wheels. Under these conditions, how much energy do we think is being dispersed as heat in the batteries due to resistive losses? Maybe a couple of horsepower? That’s 1500 watts, about the same as a good space heater. ISTM that if you put a real 1500-watt space heater in your car, it would heat things up pretty slowly. Moreover, if you’re going to use the battery’s waste heat for the cabin, then the battery has to be allowed to warm up quite a bit first - and a battery that weighs upward of 1000 pounds will take a long time to heat up using only 1500 watts of heating power.
Contrast that with my IC-engine powered sedan. Within three minutes of leaving my garage, the HVAC is starting to deliver heat. Cruising down the highway, the engine is providing 30 horsepower at the wheels, just like the Model S. But it’s also trying to dump approximately 30 horsepower of waste heat through the cooling system, and all of that waste heat is available for use by the HVAC. I doubt you’ll ever find a car with an HVAC system designed to harvest all of that waste heat, but knowing the volume and temperature of warm air that’s available when the heat and blower are maxed out, I have no doubt it’s far more than 1500 watts/2 horsepower.
I’ve seen that guide before but hadn’t read the bit about the battery cooling system. But the 12v battery must be producing some of the heating since it defrosts the windscreen while sitting still.
The whole point of the Model 3 design is simplification to reduce mass production costs. So AFAIK it only has the electric heater, no fancy plumbing to push the battery heat from the coolant into the cabin. After all, it will take a lot longer for that heat to reach useable temperature, and the whole point is that the batteries should not get excessively hot - and never not burning-carbon hot like any combustion engine. As a side note, it also does not have a coolant heater to warm the batteries like a Model S or X, relying instead on running current through the motor(s) without turning them as a means of warming the batteries. When my Model 3 has been sitting in sub-zero a few hours, I get a warning regenerative braking will not work since batteries cannot be recharged below freezing. After a decent amount of driving, that warning disappears. (With electric heat, I get warm air within 15 seconds and can pre-heat with an app on my phone)
So the vehicle is adequate in cold weather in a place that has these conditions maybe 4 months of the year; most locations don’t have these issues, and for a tracked crawler in the Antarctic, I assume, different design decisions would be required. But much of the year, it’s as good as and a lot cheaper than a gasoline vehicle.
Most of the waste heat from an ICE vanishes out of the exhaust pipe. But indeed, there is more available from cooling the engine block than cooling the batteries in an electric car. But the presence of a heat pump makes things easier. You don’t need water at near boiling point running through the pipework. On the flipside, if the battery did get that hot it would be in trouble.
Off topic but I think related question, please.
For those who charge at home, how much does your electricity bill increase relative to your gasoline bill decrease? More generally, are the cost ratios per mile traveled for electric versus gasoline remaining in favour of the former? I believe they do, but is the margin declining?
It depends - gas & electricity prices vary from state to state, and change over time. Some electric cars are more efficient than others. Same goes for gasoline powered cars.
Electric cars typically get 2 to 4 miles per kWh. So it takes anywhere from 25kWh to 50 kWh to drive 100 miles. You lose around 10% to charging inefficiency on top of that. Electricity rate in the US varies from about 9 cents to 15 cents per kWh. Which means cost to drive 100 miles varies from $2.50 (at 4 miles/kWh and 9 cents per kWh) to $8.25 (at 2 miles / kWh and 15 cents per kWh).
A 25 mpg gasoline powered car would cost $8 per 100 miles assuming $2 per gallon. A 40 mpg hybrid costs $5 per 100 miles.
You could preheat it to 100 degrees and all that heat would be gone in a few minutes on the road.
But you’d be comfortable right from the start, without having to wait for the interior to warm up.
Anyway, the real benefit to pre-heating an electric car is to warm up the battery, which makes the battery work more efficiently.
For me, preheating doesn’t seem to pull quite enough from the battery to warm it up. What does warm the battery is charging it. I schedule my car to charge to 70% starting when my low electricity rate starts, but then to charge to 75% about an hour before I leave in the morning. That means the battery has much more regen available for my morning commute.
At the temperatures I’ve been driving, these are the efficiencies I get. This is only counting drives over 10 miles. (Ignore the extra ", they’re just for formatting.) 235 Wh/mile is 100% efficiency.
Temp… Wh/Mile Efficiency% Miles Driven
15 to 20 F 322.28 “69.1 “””“”" 43.41
20 to 25 F 240.86 “94.4 “””“”" 43.76
25 to 30 F 274.29 “81.2 “””“”" 12.76
30 to 35 F 227.06 103.1 “”“”“” 44.79
35 to 40 F 254.52 “89.4 “””“”" 74.61
[FONT=Trebuchet MS]So I’m not driving in the sub-zero temperatures that some of the country has been experiencing, but I’m also certainly not seeing my range completely destroyed by normal winter temperatures. Shorter trips are much less efficient, because the heat and such runs the entire time. Of course, a 2 mile trip that uses 6 miles of battery, is not exactly going to cause range anxiety.
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