Where Ratings Come From
Understanding how EV range estimates are created is a good place to start. However, determining the actual range of an EV can be a bit confusing at first because you’re likely to see three different numbers in reference to any given vehicle. The EV range numbers you’re most likely to see are provided by three different organizations: the US Environmental Protection Agency (EPA), Worldwide Harmonised Light Vehicle Test Procedure (WLTP), and New European Driving Cycle (NEDC). Their numbers rarely line up with each other and can also differ from real world ranges because each organization has its own specific test procedures. It can be helpful to understand how each one arrives at their own results and how those results relate to EV ranges in the real world.
How the EPA Determines EV Range
The US Environmental Protection Agency conducts a number of tests that involve driving the test EV on a device that’s basically a treadmill for cars. The primary test involves simulating driving an EV at a speed of 21.1 MPH for 11.04 miles. Other tests are also performed, including one meant to simulate highway driving, and one meant to simulate stop-and-go city driving. The numbers from each test are then combined to create an estimated range. When you look at an EV range provided by the EPA, it’s important to remember that its test procedures are performed indoors at room temperature and at very specific speeds. The vehicles are also tested with only a single person inside (the driver), without additional passengers or cargo. These and other factors can cause an EPA EV range to differ from real world experiences, where drivers experience extreme heat or cold, haul lots of passengers or cargo, or keep a lead foot on the accelerator. To make it easier to understand its results, the EPA doesn’t just report range. It also provides a miles-per-gallon equivalent measurement, or MPGe, that you can compare the EPA MPG estimates given for ICE vehicles.
NEDC Vs. WLTP: The Other Range Measurements to Know
The other two EV range measurements are the New European Driving Cycle and the Worldwide Harmonised Light Vehicle Test Procedure. The NEDC was originally introduced in the 1980s, and the WLTP is designed to take its place, primarily because WLTP provides more accurate, real-world range estimates while the NEDC tests are based more on theoretical driving estimates. During the transition, it’s common to see both numbers cited when you’re comparing EVs. NEDC and WLTP tests are both performed at higher maximum speeds than the EPA test procedure. Here’s how they differ: Since the WLTP uses a longer driving cycle, includes more test phases, and takes into account other real-world factors, it provides a more complete picture than the old NEDC test.
Your Mileage May Vary: Range in the Real World
The ranges given by the EPA, WLTP, and NEDC are all useful guidelines, but they rarely line up perfectly with real world experiences. The EPA typically reports the lowest range numbers, the NEDC reports the highest, and the WLTP tends to fall in between the other two. Part of that is due to testing temperatures, as the NEDC uses the highest average testing temperatures, and batteries tend to perform better warm than cold. The rest is due to different testing procedures, as each test uses different speeds and different mixes of simulated urban and non-urban driving. Looking at an example EV (the 2019 BMW i3 BEV), you can see how the different reports vary wildly. Another tester, Inside EVs, came up with a result about 8 percent lower in its real world tests, for a range of 141. Both of these independent test results are fairly close to the EPA numbers, while the NEDC and WLTP numbers are much higher. The bottom line is that, although these ranges do give you some help in narrowing down EVs that are more appropriate for your lifestyle, many other factors should also be considered. For example, if you live in a cold area, or do a lot of winter driving in cold conditions, then you’re likely to see real world EV ranges that are significantly lower than even the EPA numbers. EV range is also impacted by running accessories like air conditioning, so the numbers you see will also end up lower than the official ratings if you run power-hungry accessories a lot. On the other hand, you might also see numbers closer to the WLTP ratings if you live in a temperate area and your driving habits closely match the program it uses for its tests. For most drivers, however, the EPA numbers are usually the closest to what you can expect to see in the real world.
