Chevy Bolt EV

Chevy Bolt EV

How did Consumer Reports evaluate the Chevrolet Bolt and the Tesla Model S, which resulted in the Bolt's range-king status?

We recently reported that, according to Consumer Reports, the 2017 Chevrolet Bolt exceeded the Tesla Model S in electric range. It's important to keep in mind that the test used a 2016 Tesla Model S 75D, and while Tesla offers variants with much more range, this still came as a surprise to many, including Tesla. The Bolt offers and EPA-estimated 238 miles of range, whereas the EPA puts the specific Model S at 259 miles.

Tesla Model S

Tesla Model S

The Bolt is officially the CR's new record-holder for all-electric range. It pulled off 250 total miles to the Model S' 235.  Though the original CR publication, as well as the video (below), seemed to do a pretty good job of explaining the testing process, CR has released another, more detailed post since Tesla recently challenged the results.

CR made it clear that Tesla offers longer range models and the Model S is still the publication's top-rated ultra-luxury sedan. CR's VP for Research, Testing, and Insights, Liam McCormack, shared:

“CR designs testing methodologies to enable the evaluation of all comparable products in a fair and standardized way. We look at the criteria which in our judgment are most important to consumers to evaluate products in an independent and fair manner.”

The most important point of CR's defense is that its objective testing process aims to replicate normal day-to-day driving. While the tests include criteria like turning off the AC and heat, keeping tires properly inflated, and starting with a full charge (all things that many people aren't likely to do), CR has no goal to set range records. Instead, the process is set up to ensure fairness, consistency, and repeatability.

CR points out specific criteria in its EV testing regimen:

  • First, we make sure the car is fully charged.
  • We check tire pressure when the tires are cold to ensure that they are all inflated to the manufacturer’s suggested settings.
  • To ensure repeatability, we turn off the heating and air conditioning system, because hard acceleration and running the HVAC system can cut the range significantly, as can driving in very cold temperatures.
  • We make sure the car is in its version of normal drive mode, not extended range mode, because our goal is not to see what’s the maximum range an EV can get when pushed to its limits, but rather to see the total number of miles a driver should expect under normal circumstances.
  • We put our EVs into their less-aggressive regenerative braking mode; regenerative brakes help EVs recapture some of the energy lost in braking. Many EVs have a mode with aggressive regenerative braking that’s meant to capture more of that energy, but it can be an intrusive experience, making the brakes seem grabby, especially for drivers who are new to EVs.
  • Our EV range test involves some mixed driving, but much of it is done by driving a constant 65 mph on highways. If drivers were to meander on rural roads at 45 mph, for example, they might get even more range.
  • We test cars when they have between 2,000 and 3,000 miles on them to assure similar levels of break-in. This is especially important as the rolling resistance for the tires can change as they wear.

Source: Consumer Reports