M3 MR vs Chevy Bolt (energy consumption)

[Dan123]

So I have been measuring the energy consumption of Chevy Bolt and M3 MR, driving the same urban route (mostly stop and go, lots of lights, average speed probably about 20 MPH). In both cases the weather is moderate, around 70-80 degrees, with minimal AC usage, and no heat. I am not relying on the car's self-reporting, but using a charger that measures the amount of energy needed to bring the car back to the pre-determined limit (hill top reserve for Bolt and 90% for M3).

Chevy Bolt consumes a lot less energy than M3. From the onset, Chevy Bolt provides you information about energy spent on driving, climate control, and battery conditioning. M3 doesn't provide this breakdown. And it appears that M3 energy calculator is very inaccurate and doesn't take into account very significant energy consumption when the car is stationary.

So for Chevy Bolt:
Total Distance: 1187 miles
Energy Consumption Per Car: 253 kWh (0.2125 kWh/mile)
Energy Consumption Per Charger: 270.86 kWh (0.2280 kWh/mile)

For Tesla M3 MR:
Total Distance: 569.7
Energy Consumption Per Car: 134 kWh (0.2352 kWh/mile)
Energy Consumption Per Charger: 167 kWh (0.2934 kWh/mile)

Trying to think of some of the reasons for this:

• For Tesla, there is a very big difference between the energy consumption reported by the car and the energy required to charge it (20%). For Bolt, the difference was only 7%. I do not think that this is just because of the inverter inefficiency, I believe the energy consumption reported by Tesla is inaccurate (understates the actual consumption).
• 
  
• The other factor appears to be that Tesla's onboard electronics (cameras, computers) have a more significant power consumption than Bolt's.
• 
  
• Tesla tires appear to provide better grip (and higher rolling resistance) than Bolt's.
• 
  
• Tesla battery conditioning appears to be more aggressive than Bolt's.

The end result, however, is not a very significant difference. If I drive 10000 miles per year, Bolt will consume 2280 kWh ($296) and Tesla M3 will consume 2934 kWh ($381).


I suspect that the result will be different during highway driving, but haven't had a chance to measure it.

 

[Daniel in SD]

Tesla takes advantage of a loophole in the EPA test that allows them to not count "vampire drain" as energy consumption. It amounts to a little more than 1kWh a day that is not measured by the test. How many days was your test conducted over?

 

[woodisgood]

Is the Bolt not significantly lighter?

 

[M109Rider]

Interesting. But I’m a little confused.
You said the bolt consumes a lot less energy, but the kWh/m are much lower on the M3 ?

I get that you’re saying it takes more kw’s during charge, but as far as consumption, the M3 seems better.

I haven’t seen any concerns about kWh/m used compared to kw’s being higher during charge before.

Do I ha e this correct, or am I off somewhere in my interpretation of your post ?

Interesting post.
Thanks.

 

[mtndrew1]

I suspect the you’re seeing the result of Tesla’s famous vampire drain in the power consumption results, as I also suspect the Model 3 will take the lead in a similar highway test.

The Bolt is a very efficient city runner.

 

[AlanSubie4Life]

Interesting data, and so we're all clear on the meter in the car on the Tesla Model 3:

The meter in the Tesla does not account for ANY energy use while the car is in Park. This is energy that is "missing" from the display, in addition to the vampire drain mentioned above (which is about 750Wh-1kWh/day - not in dispute, info is directly from Tesla) - so it would be good to know the time period of the test so as to correct for the vampire drain component (even though it definitely counts in any case!)

I have found that the meter in the car is fairly accurate with those caveats (meaning ONLY that the "since last charge" meter extrapolates to 75kWh for a full charge - of course it is possible that Tesla is fudging the absolute numbers and the actual true pack capacity - I haven't checked that). But it is definitely accurate ONLY if you spend zero time in park (and zero time with the car in the garage) since the last charge.

EDIT: To me it's a bit bizarre that Tesla doesn't allow you to track your energy use while you're parked. It causes no end of confusion for end users who aren't super detail-oriented (they just want to drive their car!) but still notice when they're not getting the range they expect. There are any number of ways they could display this information which would be easily understood by the driver.

 

[Daniel in SD]

Is the Bolt not significantly lighter?

They are almost the same. Bolt 3,563lb Model 3 MR 3,686. The Model 3 is rated at 121mpge and the Bolt at 119mpge. Mpge is supposed to measure wall to wheel efficiency but somehow does not include standby or vampire energy usage. GMs EVs have virtually no vampire drain.

 

[seattlite2004]

After about 11K miles of mixed driving, starting from March '18 till today, my '18 Bolt has the following lifetime consumption:
From the Car:
4.797954698 mi/kWh
208.422143 w/mile

From the Charger:
4.413611937 mi/kWh
229.2957598 w/mile

Delta 8.26%

 

[AlanSubie4Life]

Can you also provide some details on what your charging option was? It sounds like it was the same wall charger for both vehicles? How many amps? This is (perhaps) relevant to help understand what efficiency the Tesla Model 3 on-board charger was operating at (how many input watts). Allegedly (according to this forum) it's somewhat lower efficiency at lower current, though I don't have a convenient table at hand. As with many things on this forum, this may well be a false claim, or obfuscated by the effects of battery warming that has to take place in sub-freezing or chilly temperatures.

(Tesla's table doesn't suggest there is any significant impact on efficiency under Florida conditions...this table is somewhat subject to rounding error but we're looking for differences of more than 5% here)

Wall Connector

It's pretty easy to see this table implies charger efficiency of 94-96% (using the Model 3 column and the magic (possibly incorrect) 242Wh/mi constant). I wonder what it actually is? Does anyone know the published efficiency of the Bolt on-board charger?

 

[brkaus]

I’m not surprised for urban comparison.

 

[gaswalla]

Very interesting.
I bet with chill mode on and measurements made for individual routes, Model 3 would come out close or better. Vampire drain does affect numbers presented by OP; on the other hand, why can't Tesla get vampire drain down to the level of the Bolt? It is electricity that one needs to replenish.

 

[AlanSubie4Life]

bet with chill mode on and measurements made for individual routes, Model 3 would come out close or better.

Other than on the highway, I doubt it. And chill mode should have zero effect on efficiency with baseline efficiency numbers like this. Chill mode doesn't make any difference to efficiency as far as I know (if you're trying to drive efficiently). I'd be very very surprised if it did. It just limits the peak current and you can still go 0-60 in 7 seconds or so. And if you're accelerating that fast you're not trying to drive efficiently. Need to keep I^2*R losses to a minimum.

 

[Daniel in SD]

why can't Tesla get vampire drain down to the level of the Bolt? It is electricity that one needs to replenish.

Why do cable boxes use 50W when they're off? That's what's so insidious about vampire drain, it's hardly ever an engineering priority and most people don't notice but when you add it all up it's a significant portion of this countries electricity usage.
I bet if it were included in the MPGe number Tesla would fix it.

 

[AlanSubie4Life]

Why do cable boxes use 50W when they're off? That's what's so insidious about vampire drain, it's hardly ever an engineering priority and most people don't notice but when you add it all up it's a significant portion of this countries electricity usage.
I bet if it were included in the MPGe number Tesla would fix it.

I think my cable box/DVR is down to a mere 22W. The full weight of Samsung's engineering resources over 10 years accomplished that. It is so difficult! Can you imagine what will happen when they go to SSDs for the DVRs? They might be able to get it down to a mere 10W! Awesome.

Anyway, that makes the Tesla the worst offender in my house (other than my A/C unit crankcase heater).

 

[mtndrew1]

@M3BlueGeorgia what exactly are you disagreeing with in my post?

Vampire drain is not counted on the instrumentation and explains the disparity in total power dispensed from the wall.

Do you have evidence to the contrary?

 

[AlanSubie4Life]

Along the lines of the "standby" drain (not vampire/phantom) @Daniel in SD mentioned above:

Another interesting factor I was thinking about yesterday, related...it seems that the Tesla baseline usage is at least 400W just sitting there with just the screen on (you see ~500W draw from the wall charger in that scenario (2A @ 240V), so multiply by efficiency of 0.94). I'd bet the Bolt has a lower baseline usage. For an average speed of 20mph, that's an additional 20Wh/mi, that hurts the Tesla.

So there's actually significant savings available for Tesla there (which they are not taking), if that 400W is anywhere close to correct. Personally I'm hoping for a software update, though it's probably hardware limited. Tesla has such an efficient drivetrain it's odd that they allow such a high baseline load - would be better to have baseline be less than 5% of the energy you're using to go 20mph. Below that and it starts to not matter much. My number might be wrong for whatever reason though (and there is potentially significant rounding error; the 2A at 240V indicated might be closer to 1.5A at 240V, which would put the baseline load at less than 350W). It's also possible there are other things going on that draw that 2A from the wall connector/UMC when plugged in - like the charger, for example, may be very inefficient there, and the true baseline load may be a lot lower. Very hard to say (the experiment would be to sit in the car for a long, long time, in drive, while not moving, with heat & A/C off, and see how many miles you lose).

 

[Az_Rael]

Is the Bolt not significantly lighter?

I think the MR RWD is actually lighter than the Bolt.

 

[Dan123]

Tesla takes advantage of a loophole in the EPA test that allows them to not count "vampire drain" as energy consumption. It amounts to a little more than 1kWh a day that is not measured by the test. How many days was your test conducted over?

Months. Yet, vampire drain is very noticeable on a Tesla, and practically non-existent for Bolt.

 

[Dan123]

Is the Bolt not significantly lighter?

No, maybe 100-200 pounds lighter.

 

[Dan123]

Interesting. But I’m a little confused.
You said the bolt consumes a lot less energy, but the kWh/m are much lower on the M3 ?

I get that you’re saying it takes more kw’s during charge, but as far as consumption, the M3 seems better.

I haven’t seen any concerns about kWh/m used compared to kw’s being higher during charge before.

Do I ha e this correct, or am I off somewhere in my interpretation of your post ?

Interesting post.
Thanks.

Bolt was 0.2280 kWh/mile
Tesla was 0.2934 kWh/mile