Here’s How To Calculate Conflicting EV Range Test Cycles: EPA, WLTP, NEDC

from left: Tesla Model S, Tesla Model 3 and Tesla Model X

MAR 7 2019 BY DAVID ROPER 26

Now, you can more easily compare EV range figures from various test cycles.

Articles about electric vehicles (EVs) are confusing with regard to range estimates. The confusion is because U.S. Environmental Protection Agency (EPA) estimates are considerable smaller than the original New European Driving Cycle (NEDC) estimates, and the because the legal European estimate is changing to Worldwide harmonized Light vehicles Test Procedure (WLTP), whose magnitude is between EPA and NEDC. All new-car registrations in Europe from September 2018 are required to use WLTP range estimates.

I have collected EPA and NEDC estimates for six BEVs and the average ratio NEDC/EPA is 1.428 with a standard deviation of 0.161. So, U.S. BEV/PHEV drivers can convert NEDC range estimate to approximate EPA range estimates by dividing the NEDC value by 1.43 with an 11% error.

I have collected EPA and WLTP range estimates for nine BEVs and the average ratio WLTP/EPA is 1.121 with a standard deviation of 0.092. So, U.S. BEV/PHEV drivers can convert WLTP range estimate to approximate EPA range estimates by dividing the WLTP value by 1.12 with an 8% error.

Of course, the EPA range estimate is, indeed, an estimate.

Editor’s Note: This article comes to us as a free contribution from our good friend L. David Roper.

L. David Roper, roperld@vt.edu, roperld.com/personal/RoperLDavid.htm

Categories: EV Education, General

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26 Comments on "Here’s How To Calculate Conflicting EV Range Test Cycles: EPA, WLTP, NEDC"

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Very useful formula! Thanks, David!

Thank you! I’ve been looking for just this!

Just remember that NEDC stands for “Not Even Darn Close”, and you’re good to go. 😛

😀

Luckily, is outdated and will not be used anymore.

Thank you for this. Whoever thought that the EPA estimates would be the most conservative? Your mileage may vary.

It is only conservative for EVs. ICE milage is very optimistic. This is to keep ICE looking better compared to EVs.

EPA is actually pretty accurate for EVs when temperature/terrain are included. It is far close to “average real world” usage.

ICE EPA figures are optimistic.

They should add some climate numbers too, in order to help people understand lower range, especially while very cold.

It becomes too subjective. Cold weather range depends on how high you keep the thermostat.

Exactly. It’s surprising to me that the EPA has never adjusted its gasmobile MPG testing cycle to conform more closely to real-world range, as it has with its EV range ratings.

Thanks to David Roper for this work.

Now will European OEMs stop using NEDC already!?

Since september 2018, any new car must be homologated under WLTP. NEDC remains for older cars for some years, but there are no much because almost all cars in Europe upgraded their engines before that date and are WLTP compliant.

And good news, Euro Ncap, has launched a new assestment protocol, Green Ncap. Now they will test cars for analyze their efficiency and enviromental impact using more accurate and severe tests than official WLTP. For example they use WLTP protocols, but they make the normal test but they add four test more, a cold test, a test in ECO mode, another one in Sport mode and finally, a test under high load, a Highway test simulating 130 km/h and some accelerationss from 80 to 130 km/h.

You can see more in its website.

http://www.greenncap.com

Nice work, thanks. I have been calculating an estimate for the WLTP/EPA by dividing the WLTP by 1.1, so I was pretty close without doing the work. 🙂

The EPA range estimate is the only one that comes close to real world use. With factory tires my chevy bolt gets slightly better than the EPA range estimate and my Toyota Mirai gets slightly lower than the EPA range estimate.

Yip, easiest method is to ignore everything else and only compare EPA figures.

Sometimes, on new cars, we only have the WLTP until the EPA does their duty.

This makes it sound like it was on EPA… It’s actually on the car makers to go through the certification process.

Real World: EPA x 0.85.
Winter: Real World x 0.65.

Thank you David Roper! These conversion factors will be quite useful.

“…the average ratio WLTP/EPA is 1.121 with a standard deviation of 0.092.”

Good to see the standard deviation with WLTP is significantly less, by about a third, than the standard deviation for NEDC. That was the primary problem with NEDC; that it was so easy to “game the system” that, even aside from being inflated, the number was so far off that it wasn’t of much use even as a comparison to other EVs.

WLTP ratings still aren’t nearly as accurate as EPA ratings, but at least they are a significant improvement over NEDC.

you forgot the TBTP, the most realistic of them all

There is also the Japanese JC08.

How often do you have to deal with range figures given according to JC08, though?…

Why does the EPA continue fake testing of energy usage? No real roads are driven. Shameful and dishonest to the public.

How do you standardize a real road? You forget thAt they need to define a test that is repeatable and consistent. You cannot control for wind direction, temperature, etc on a real road.

Same as exchange rate usd/eur 😉

Nice Info.
For EVs I have found the EPA rating the closest to your real world usage.
The NEDC is more or less a lab test under well controlled conditions, and creates values that are far away from the real results. Is teh same on ICE cars there. The consumption on the NEDC rating you can only reach if you shut down the engine and let teh car roll down a hill.
WLTP is a step in the right direction but still way to optimicstic.