Bolt Efficiency, How Accurate?

[Arob216]

I have put 5100 miles on my Bolt. I mainly use it to commute 125 miles per day and end up with high 4 or low 5 mi/kWh efficiency. I typically use 25 kWh of energy each commute day, so in the 35 or so days of commuting, I estimate using somewhere in the neighborhood of 750 kWh to charge the car since I bought it. Based on a generous assumption of 1000 kWh used since I bought it, my average would be around 5.1 mi/kWh.

So, first let me say that it is not easy to get a good view of efficiency and power use with the tools GM provides. As I understand, there are three, the on-dash Energy stats, the myChevrolet Smartphone app, and the myChevrolet web portal. All seem to give incomplete, disparate or inaccurate views of things.

For example, the smartphone app reads a lifetime efficiency of 3.9 mi/kWh, but my dead reckoning is it is in fact closer to 5 mi/kWh. The web portal is absolutely incomprehensible, displaying the following:
Lifetime/ Last 30 days
Electric Miles 5,121 / 2,175
Electric Economy 25 Kwh/100mi / 10,396 Kwh/100mi
Electricity Used 192 Kwh / 478 Kwh
Est Fuel Saved 197 gal / 84 gal
Est. CO2 Avoided 3,821 lbs / 1,646 lbs

And, the dashboard only provides current data since last full charge.

So, my question is, how do you assess your efficiency? Am I correct in assuming none of these is terribly accurate? How do I even make sense of the web portal data (the numbers seem to be pulled out of the blue)? Am I missing something?

My EVSE is not smart, so I have no way of gleaning stats from it, nor are my utility companies records of much use.

 

[SeanNelson]

The most accurate way I know of is to use the "kWh used" value in the "Energy Info" display on the centre screen. It supposedly shows the energy drawn from the battery that's used for any purpose, including propulsion, HVAC and battery conditioning.

You have to add a fudge factor to that to account for the fact that the car's built-in charger isn't 100% efficient, so it draws more power from the wall than it delivers to the vehicle. If you had an energy meter wired to the outlet you use to charge the car then that would give you the most accurate figure.

 

[paulgipe]

That's what I do. I also have a kWh meter. I track both. I could post a spreadsheet if that would help.

Paul

 

[Arob216]

The most accurate way I know of is to use the "kWh used" value in the "Energy Info" display on the centre screen. It supposedly shows the energy drawn from the battery that's used for any purpose, including propulsion, HVAC and battery conditioning.

You have to add a fudge factor to that to account for the fact that the car's built-in charger isn't 100% efficient, so it draws more power from the wall than it delivers to the vehicle. If you had an energy meter wired to the outlet you use to charge the car then that would give you the most accurate figure.

So, jot down the details daily (or every time you charge it) and plug them into a spreadsheet?

 

[paulgipe]

Yes.

 

[mgoleta]

We did the experiment today with our 2018 Bolt. Start of trip, predicted 256 mi predicted range. We drove 121 miles using a reported 29.1KWhr. It reported an average 4.2mi/kWhr. The reported remaining range at the end of the trip was 130 mi. These number seem very consistent with having a 60KWhr battery. This appears far more accurate than our 2011 LEAF ever was (it is terrible at predicting real range). I have not yet done the experiment with our new 2018 LEAF (only 2 days old).

 

[Arob216]

That's what I do. I also have a kWh meter. I track both. I could post a spreadsheet if that would help.

Paul

Curious about your findings of kWh meter vs spreadsheet. I assume this would indicate the actual power used during charging, including any loss due to resistance, battery conditioning, etc, How much difference do you find? I have heard estimates between 15-30% more power is used in charging than the car reports as the car really only reflects based on SOC. I imagine the variance is greater in colder winter months when conditioning is more common?

I put a spreadsheet together to track commute efficiency only, since 99% of my Bolt use is commuting. I capture kWh used, and mile to work, and total since last charge and it calculates mi/kWh and shows the difference between to and from by calculating the total - to work figures. I find it is pretty close to the mi/kWh the car displays, typically the variance is +-.1 mi/kWh, likely due to rounding.

My results are impressive, at least in summer months. I average 6.6 mi/kWh on the leg to work (2300 foot elevation drop), 4.0 return trip for a 4.9 average daily. Surely this will drop in winter months, but clearly better than the estimates. I calculate this to be 166 MPGE based on an estimate of 33.7 kWh = 1 gallon of gas.

 

[paulgipe]

That's what I do. I also have a kWh meter. I track both. I could post a spreadsheet if that would help.

Paul

Curious about your findings of kWh meter vs spreadsheet. I assume this would indicate the actual power used during charging, including any loss due to resistance, battery conditioning, etc, How much difference do you find? I have heard estimates between 15-30% more power is used in charging than the car reports as the car really only reflects based on SOC. I imagine the variance is greater in colder winter months when conditioning is more common?

I put a spreadsheet together to track commute efficiency only, since 99% of my Bolt use is commuting. I capture kWh used, and mile to work, and total since last charge and it calculates mi/kWh and shows the difference between to and from by calculating the total - to work figures. I find it is pretty close to the mi/kWh the car displays, typically the variance is +-.1 mi/kWh, likely due to rounding.

My results are impressive, at least in summer months. I average 6.6 mi/kWh on the leg to work (2300 foot elevation drop), 4.0 return trip for a 4.9 average daily. Surely this will drop in winter months, but clearly better than the estimates. I calculate this to be 166 MPGE based on an estimate of 33.7 kWh = 1 gallon of gas.

I was referring to wall source to battery efficiency. It averages about 92% to 94%. Here's some numbers.

0.93
0.64
0.94

0.94
0.79
0.78

0.92
0.95

0.94
0.94

0.93
0.92
0.94
0.96

0.92

0.90
0.92
0.81

0.94

0.94
0.86
0.92

There are some anomalies but typically 92 to 94.

That's not a "revenue grade" kWh meter but should be good enough for this purpose.

Paul

 

[Arob216]

I was referring to wall source to battery efficiency. It averages about 92% to 94%.

There are some anomalies but typically 92 to 94.

That's not a "revenue grade" kWh meter but should be good enough for this purpose.

Paul

Thanks, that is helpful. I would imagine lower efficiency in extreme weather when conditioning and pre-conditioning are used.

 

[scooter123]

around town on a cool day I can get 5.2-5.3 miles per KWh.
I drive for Uber/Lyft.

 

[Maxters]

The most accurate way I know of is to use the "kWh used" value in the "Energy Info" display on the centre screen. It supposedly shows the energy drawn from the battery that's used for any purpose, including propulsion, HVAC and battery conditioning.

You have to add a fudge factor to that to account for the fact that the car's built-in charger isn't 100% efficient, so it draws more power from the wall than it delivers to the vehicle. If you had an energy meter wired to the outlet you use to charge the car then that would give you the most accurate figure.

Best way for me, since I only charge at home, is to look at the juicebox kWh that was put in. That would include the loss while charging.

 

[paulgipe]

I was referring to wall source to battery efficiency. It averages about 92% to 94%.

There are some anomalies but typically 92 to 94.

That's not a "revenue grade" kWh meter but should be good enough for this purpose.

Paul

Thanks, that is helpful. I would imagine lower efficiency in extreme weather when conditioning and pre-conditioning are used.

I'll know more at the end of the summer, right now I am looking at 84% with conditioning.