Bolt winter performance, an ICE comparison

[winterescape]

We have both a Bolt and a two year old ICE vehicle and we, for some reason, live in upstate NY. I have tracked MPG of the various vehicles we have owned, all posted on fueleconomy.gov

I thought I might do a quick comparison of the fuel economy hit in the winter between our current ICE to our Bolt.
ICE = EPA rated at 26MPG, Vehicle has 40K miles and is 2 years old. Vehicle lifetime average is shown at 26.5MPG
I selected a few frigid times where I had concurrent fuel up data for the ICE
1/14/16 = 21.3 (cold & remote start used)
1/22/16 = 19.7 (bitter cold and remote start used)
3/7/2016 = 21.6
12/20/16 = 21.6
12/14/17 = 22.8 (cold but no remote start)

Avg = 21.4 / 26.5 = 19% drop from average in cold weather

Bolt EPA 238Miles, observed low point 172 miles when full, vehicle plugged into a level 2 charger in a hotel parking lot overnight, temps dropped into the 20’s but warmed to freezing by departure time, similar data point with Bolt in garage (34 deg) and outside temps in the teens for the last several drive cycles. Cabin temp set to 72, like to use the "precondition" feature before driving, seat heaters on "auto" frequent use of heated steering wheel (what a great feature)

172/238 = 28% drop from average in cold weather


Observations:
1) The Bolt DTE “distance to empty” being prominently displayed makes the driver keenly aware of the reduced distance in the winter, contrast this to the ICE where just the gas level is displayed, so the driver has no idea that the distance to empty has dropped off by 20%. No one monitors the DTE screen on an ICE vehicle, no one.

2) With the lack of significant waste heat, the battery characteristics, and resistive cabin heating, the Bolt DTE falls off by a larger % than an ICE vehicle in the cold weather, but not by an unreasonable amount.

Conclusion: Stay warm this winter, enjoy your Bolt, and think Spring!

 

[LeftieBiker]

At some point GM is going to have to offer a heat pump, if not on the Bolt then on their upcoming E-SUV. As more 200+ mile electric vehicles enter the market, Winter range will become a bigger selling point.

 

[BarfOMatic]

At some point GM is going to have to offer a heat pump, if not on the Bolt then on their upcoming E-SUV. As more 200+ mile electric vehicles enter the market, Winter range will become a bigger selling point.

The colder it gets outside, the less effective a heat pump is. In heat mode, it is basically being an air conditioner in reverse, extracting what heat it can from the outside air and transferring it to the indoors. The less heat available outside, the cooler the air coming out the vents inside. Heat pumps do best when it is above freezing and when the difference between the temperature outside and what the thermostat is set at is 10-15 degrees. So while a heat pump would be *great* from *my* point of view (in my part of the west coast, winter daytime temps are generally between 45-65), in upper NY State, having just a heat pump wouldn't be anywhere near sufficient.

Offering an option of an additional heat pump (in addition to the resistive heater) for $1500-$2000 would be a good thing, IMO.

 

[LeftieBiker]

That was pedantic, as no manufacturer offers ONLY a heat pump. They are always in combination with a PTC heater. I have actual experience with a heatpump-equipped system in Upstate NY, and it really helps the range down to about 25F, and makes some difference down to about 15F. That means that for roughly 90% of the year it increases my Leaf's range significantly. The problem with PTC heaters is that they suck power in large amounts regardless of the weather. So when you turn on the heat to defog the windshield on a chilly but not cold morning, you are sapping the vehicle's range much more than would a "hybrid" heatpump-PTC system. What I wrote stands.

 

[GetOffYourGas]

When I had a 24kWh Leaf, I longed for a heat pump. Now I have a 60kWh Bolt and I could hardly care less. Yes, it uses more energy but so what? I'm rarely driving that deep into my battery. It just means it takes slightly longer to recharge (which happens while I'm working anyway).

There was an article written a few years back which showed that an EV's relative fuel saving increased during the winter. It is counter-intuitive, but the math works out. Basically, the fuel usage goes up by a larger percentage, but since it started out as a smaller number, it goes up by a smaller absolute cost. I wish I could find the article, but I don't even remember which site I read it on.

Unrelated to heat/range in the cold, there is a solid benefit to an EV - they don't lose driving performance in the cold. An ICE needs to warm up its engine before you demand anywhere near full power. An EV is ready to go, especially the Bolt with its thermally managed battery. I was able to get 145kW out of a cold-soaked Bolt (single-digit F) right from the get go. Couldn't do that in an ICE.

 

[LeftieBiker]

Yes, it uses more energy but so what? I'm rarely driving that deep into my battery. It just means it takes slightly longer to recharge (which happens while I'm working anyway).

I assume that you know that individual range needs vary, but this is why I wrote that GM will need to offer a heatpump equipped heater in their upcoming SUV: the Bolt has range to spare for most needs. The E-SUV will, especially if it uses the Bolt powertrain, have less range to begin with than the Bolt, and so the Winter range drop will bring it lower towards 100 miles - especially if it has a transmission-based AWD system. Why not just have four wheel-motors? For one thing, that isn't what the Bolt uses, and GM will be looking for economies of both scale and simplicity.

 

[GetOffYourGas]

Yes of course everyone's needs vary. You, for one, are surviving with a Leaf. A Bolt has far more winter range than a 2017 Leaf, even though the Bolt doesn't have a heat pump. 2018 Leafs are a different story, but we know you don't have one of those (yet, anyway). GM may or may not eventually go with a heat pump. Harping on them for excluding it from the Bolt feels kind of silly.

Regarding a future BEV SUV, I really doubt that they would go with a transmission-based AWD. Tesla has shown that using two motors with different gearing can improve efficiency. Traditionally, AWD systems decrease efficiency. I also doubt they would put the same battery in a larger car. I'm betting they scale up the battery as needed to maintain a decent driving range. Time will tell which of us is right.

 

[EldRick]

Let me summarize: heat-pumps don't work worth a darn in weather colder than freezing, which afflicts most of the US.
That is why every heat-pump home furnace in the world also has a secondary heat source: a gas or hot-wire electric heater component, to take over from the heat-pump when it's cold out.
So there is very little point in a heat-pump in a car. It would add mechanical components that add cost and wear out and break, and would only save a bit of energy for those in California-mild climate.
The only reason the Leaf has one is because they had a tiny battery, and needed to save every possible watt-hour to provide any interior heat at all.

 

[winterescape]

Let me summarize: heat-pumps don't work worth a darn in weather colder than freezing, which afflicts most of the US.
That is why every heat-pump home furnace in the world also has a secondary heat source: a hot-wire electric heater component, to take over from the heat-pump when it's cold out.
So there is very little point in a heat-pump in a car. It would add mechanical components that add cost and wear out and break, and would only save a bit of energy for those in California-mild climate.
The only reason the Leaf has one is because they had a tiny battery, and needed to save every possible watt-hour to provide any interior heat at all.

Cost/ complexity/ reliability/ time to market VS potential benefit

As I posted in another thread where this came up, someone pointed out that BMW, KIa, and Nissan all had a heatpump. I hypothesized that GM invested in a bigger battery over the heatpump. Even though I live in upstate NY, I think that was likely a good trade.

I will however add that I am warming to the idea of a "EV cold weather package" option. This might include a heatpump and a more aggressive battery warming algo, among other optimizations for those of us that experience fewer extreme high temps and more extreme cold temps. As highlighted above, I would need GM to quantify the potential benefit to me in investing extra for that package.

 

[LeftieBiker]

Let me summarize: heat-pumps don't work worth a darn in weather colder than freezing, which afflicts most of the US.
That is why every heat-pump home furnace in the world also has a secondary heat source: a hot-wire electric heater component, to take over from the heat-pump when it's cold out.
So there is very little point in a heat-pump in a car. It would add mechanical components that add cost and wear out and break, and would only save a bit of energy for those in California-mild climate.
The only reason the Leaf has one is because they had a tiny battery, and needed to save every possible watt-hour to provide any interior heat at all.

Let me summarize: you are mistaken. Heat pumps are useful down to almost ten degrees below Freezing, and this means that they will be useful for about 90% of the year - 100% in many climates. GM chose to do without one to save themselves money, not because "there is very little point in a heat-pump in a car." It's kind of sad to see people rationalizing every mistake or cheap-out that GM commits. The Bolt is a very good little car. If they fix the seats, road noise, and wasteful heating system it will become a great little car.

 

[winterescape]

Heat pumps are useful down to almost ten degrees below Freezing

While true that heat pumps operate down to temperatures below freezing you appear to have left off the part about diminishing returns. While a heat pump will "work" it becomes far less efficient as the temperature falls. Just as your heat load increases, due to the drop in temperature, your heat output from your heater decreases. Not ideal.

We have a heat pump in our home, but I have it programed to switch to gas heat at 35 deg. Why switch that high? Defrost mode. The heat pump coil freezes up from the moisture in the air as it is trying to move the heat from outside to inside. The heat pump goes through a "defrost cycle" just like your refrigerator, It does this by reversing the refrigerant flow. Yep, it goes into air conditioning mode in the winter to melt the frost from the outdoor coil using the heat from the house. Defrost mode significantly impacts efficiency.

 

[GetOffYourGas]

It's kind of sad to see people rationalizing every mistake or cheap-out that GM commits.

This is a misrepresentation of my (and others') argument. It's not a mistake or a cheap-out. It's a trade-off. The Bolt is pricey for what it is (a compact hatchback). The reason is the large battery. GM certainly could have put a heat pump in the Bolt. IMO, that would have been a mistake. It would have made the car even pricier with little benefit.

BTW - I live in upstate NY too. I certainly do not use heat "90% of the year". The heat pump in the Leaf makes the A/C less efficient (due to engineering trade-offs). So in effect, the ~ 25% of the year that I use A/C, the heat pump is a small detriment.

The Bolt is a very good little car. If they fix the seats, road noise, and wasteful heating system it will become a great little car.

Agreed in that these things will make it more appealing to the mainstream consumer. I like the Bolt how it is, and would probably like it less if they made the trade-offs to "fix" the "problems" you have listed.

 

[LeftieBiker]

BTW - I live in upstate NY too. I certainly do not use heat "90% of the year". The heat pump in the LEAF makes the A/C less efficient (due to engineering trade-offs). So in effect, the ~ 25% of the year that I use A/C, the heat pump is a small detriment.

You're right on that. However, I use the heat about 8 months out of the year, and the drop in A/C efficiency is small compared to the gain in heating efficiency. The benefit from the heat pump is very real. Vehicles with only resistance heat see a significant drop in range every time the Defrost/Defog function is used for more than a few seconds.

 

[gessner17]

Heat pumps are useful down to almost ten degrees below Freezing

While true that heat pumps operate down to temperatures below freezing you appear to have left off the part about diminishing returns. While a heat pump will "work" it becomes far less efficient as the temperature falls. Just as your heat load increases, due to the drop in temperature, your heat output from your heater decreases. Not ideal.

We have a heat pump in our home, but I have it programed to switch to gas heat at 35 deg. Why switch that high? Defrost mode. The heat pump coil freezes up from the moisture in the air as it is trying to move the heat from outside to inside. The heat pump goes through a "defrost cycle" just like your refrigerator, It does this by reversing the refrigerant flow. Yep, it goes into air conditioning mode in the winter to melt the frost from the outdoor coil using the heat from the house. Defrost mode significantly impacts efficiency.

I have the same setup at home and i'm convinced that most people that are desiring a heat pump in the Bolt don't have one at home or have never used one. Heat pumps heat slowly and if it was cold outside, 32 or below, the air coming out of your vents would not be very warm and cozy like you want on a cold day. Especially if it was outside and the heat pump had to warm all the vents up slowly. When my heat pump at home kicks on when below 32, it takes a long time to just get the ducting warm and you never get "hot" air out of the vents. It raises the temp of the input air by 10-12 degrees at most when in the lower digits, if that temp outside is in the teens, less. I have mine set to switch over to gas at 38 due to price of natural gas here, it's just not efficient to heat with heat pump below that. The other thing would be defrost, heat pump won't pull moisture out of the air so i think when the defrost is on, you'd need element heating and then A/C which defeats a lot of the purpose of using heat pump. That being said i love my heat pump at home for mild weather but I honestly don't see the cost/benefit of it in a car. That is a lot of complexity there to break when if you truly think about it, how much efficiency would you really gain when considering everything? (window defrost, heat pump defrost mode in <32, cold weather, how much you use the heat in mild weather).

 

[GetOffYourGas]

In his defense, Leftie drives an EV with a heat pump. His experience is much more applicable than yours.

 

[marshallinwa]

If this article is correct, then it appears Toyota is sold on using heat pumps.

https://www.greencarreports.com/news/1110627_how-does-the-heat-pump-work-in-a-toyota-prius-prime-plug-in-hybrid

 

[NeilBlanchard]

If EV designers put direct heating windshield defrosters in their cars (like the e-Golf, or like Ford in the 1980's) ,then that would negate a big reason for using the heat at all.

The e-Golf has excellent front seat heaters - FAR more powerful than the Bolt EV's, and so the need for the heat pump is reduced to only a few weeks a year, here in New England. The e-Golf, however, lacks a heated steering wheel, and the rear seats are not heated, either. Like all responsibly implemented heat pumps, it transitions to resistance heat as the air temps drop below about 20F.

People might want to think about wearing a heated motorcycle vest / jacket, and use 75-100 watts (at most) rather than firing up the 3,000-5,000 watt cabin heater.

 

[oilerlord]

People might want to think about wearing a heated motorcycle vest / jacket, and use 75-100 watts (at most) rather than firing up the 3,000-5,000 watt cabin heater.

Neil, I think this is the kind of post that Leftie is referring to. We justify cheap workarounds on a $40,000 car to solve issues when an automaker could have simply designed it right in the first place. The Bolt initially fires up 9000 watts regardless if it's 30 degrees or -30 degrees, if a heat pump mitigates the energy consumption of heating the cabin - regardless of the law of diminishing returns - isn't that a good thing?

Nissan & Kia could have gone with the "most of these are going to California anyway" attitude that seems to prevail in other manufacturers of electric vehicles. They didn't. That is a good thing.

 

[LeftieBiker]

Thank you, Oilerlord. I'm going to be posting here less, now that I'm sure I'll be leasing a 2018 Leaf rather than a 2017 Bolt, but it's hard to resist talking about things that are applicable to all EVs. Like this:

I have the same setup at home and i'm convinced that most people that are desiring a heat pump in the Bolt don't have one at home or have never used one. Heat pumps heat slowly and if it was cold outside, 32 or below, the air coming out of your vents would not be very warm and cozy like you want on a cold day. Especially if it was outside and the heat pump had to warm all the vents up slowly. When my heat pump at home kicks on when below 32, it takes a long time to just get the ducting warm and you never get "hot" air out of the vents. It raises the temp of the input air by 10-12 degrees at most when in the lower digits, if that temp outside is in the teens, less. I have mine set to switch over to gas at 38 due to price of natural gas here, it's just not efficient to heat with heat pump below that. The other thing would be defrost, heat pump won't pull moisture out of the air so i think when the defrost is on, you'd need element heating and then A/C which defeats a lot of the purpose of using heat pump. That being said i love my heat pump at home for mild weather but I honestly don't see the cost/benefit of it in a car. That is a lot of complexity there to break when if you truly think about it, how much efficiency would you really gain when considering everything? (window defrost, heat pump defrost mode in <32, cold weather, how much you use the heat in mild weather).

EV heat pumps are ALWAYS, as I have written before, combined with PTC (resistance) heaters in EVs as well. The two work together, varying their contributions according to what is best for a given situation. You say that I haven't taken into account diminished heatpump efficiency below 32F. In fact I have, but I'll make it more clear. Leaf drivers have found that the particular setup we have in our heatpump-equipped Leafs stops giving a range advantage over PTC-only Leafs at about 14F. It's not a matter of the heatpump starting to use more energy than the PTC - that never happens. Instead, the PTC contributes more and more heat to the system, until at about 14F it is providing the lion's share of heat. The heatpump shuts off at about 7F, IIRC, but by then you don't notice any extra range from it.
Here are my observations about Leaf heatpump usefulness:

* 45F and above: the car loses no more range to heater use than it does in hot weather to A/C use, generally two or three miles less on the Guess O Meter. This is vastly better than using just PTC heat!

* 45F - ~39F: roughly 5 miles of range lost, even though the GOM doesn't usually reflect this. Still much better than PTC only.

* 39F - ~30F: roughly 7 miles of actual range loss. Still only about 2/3 as much power used, compared to PTC.

* 30F - 24F: roughly 10 mile range loss. AT this point you know that you're losing lots of range to heat, but it is still less than PTC-only Leafs.

* 24F - 14F: roughly 15 mile range loss. A small advantage remains, but it is just a few miles of range.

*14F and lower: indistinguishable from PTC-only heat. Roughly 20 miles of range (about 33%) lost compared with no heat. This is from a total range of maybe 65 miles, real world.

 

[winterescape]

Thank you, Oilerlord. I'm going to be posting here less, now that I'm sure I'll be leasing a 2018 Leaf rather than a 2017 Bolt,

What is nice is we now have a choice of EVs. If the lower range Leaf works for you that is great. While I greatly admire the Leaf and they obviously work for a lot of folks, I could not adapt to the limited range and had never considered one. Competition is great, I believe that we will quickly see a lot of feature cross pollination between GM / VW / Nissan/ Kia/ BMW and Ford