Most efficient highway cruise speed?

[Tim]

Hey MME Folks,

This is my first electric car, and so far it's great. Anyway, I'm getting ready to go on a road trip next month was was wondering if there is a particular speed that maximizes efficiency? Any intel from more experienced electric car folks would be greatly appreciated. Thanks!

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[MarkP213]

Glad you asked. I was wondering the same thing. I’m assuming there’s a sweet spot for the electric motors, but I have no idea!

 

[ARK]

This is my first EV as well, but I believe slower is better. At least, if there is a sweet spot that isn’t the slowest possible speed, it’s definitely not at a highway speed, so chugging along in the slow lane at 50mph would seem to be a good idea if you are dicey on whether your range will make it and need to maximize it.

 

[Luke]

Hey MME Folks,

This is my first electric car, and so far it's great. Anyway, I'm getting ready to go on a road trip next month was was wondering if there is a particular speed that maximizes efficiency? Any intel from more experienced electric car folks would be greatly appreciated. Thanks!

There was a discussion on that here before, I think Sergio mentioned 64mph was the sweet spot for him. But a lot of things can affect EV efficiency, not just speed. Things like external temperature, head wind and elevation all affect the efficiency.

 

[ChasingCoral]

Hey MME Folks,

This is my first electric car, and so far it's great. Anyway, I'm getting ready to go on a road trip next month was was wondering if there is a particular speed that maximizes efficiency? Any intel from more experienced electric car folks would be greatly appreciated. Thanks!

Sure, the slower the better. In any car, increasing drag dramatically impacts efficiency above 50 mph. Here's an ICE car graphic to give you an idea. While the units are mpg, the impact on efficiency will be similar in BEVs, with the impact on range being even more dramatic.

Fortunately, the Mach E's aerodynamics are good, so the impact isn't as severe.

EPA range estimates use a 59 mph speed. Driving over 70 can reduce range by up to 20% relative to EPA ratings.

 

[Luke]

Glad you asked. I was wondering the same thing. I’m assuming there’s a sweet spot for the electric motors, but I have no idea!

Most EVs have the best efficiency around 35mph, not a fun speed to drive in highway. Use back roads instead

 

[ChasingCoral]

This is my first EV as well, but I believe slower is better. At least, if there is a sweet spot that isn’t the slowest possible speed, it’s definitely not at a highway speed, so chugging along in the slow lane at 50mph would seem to be a good idea if you are dicey on whether your range will make it and need to maximize it.

Unlike ICE cars which have a multi-speed transmission, the Mach E is a single speed. That will change the efficiency dynamics.

 

[sockmeister]

Efficiency at speed largely depends on the aerodynamics, but for most EVs, the speed at which idle losses are overcome and before air resistance becomes significant, is around 30mph. It drops in a somewhat linear fashion after that until about 70mph, at which point it starts to drop more rapidly.

So, the short answer is, 30 mph.

 

[ChasingCoral]

Here's an article with speed impact on range and efficiency curves in Tesla MS and MX.
https://cleantechnica.com/2018/07/15/tesla-range-plotted-relative-to-speed-temperature-graphs/

 

[sockmeister]

Here's an article with speed impact on range and efficiency curves in Tesla MS and MX.
https://cleantechnica.com/2018/07/15/tesla-range-plotted-relative-to-speed-temperature-graphs/

I extracted the range vs speed WRT temperature chart from that article.

 

[HuntingPudel]

If the only power draw on the main battery is for propulsion, slower is better. In the real world, there are thousands of parasitic micro-draws on the main battery, so those have to be balanced out with the power used for propulsion. The most efficient speed *should* be the speed at which parasitic draws are just eclipsed by the power needed by propulsion. For me on an average day that would probably be a lower speed than it would be for me on a crazy hot day if I were using the climate control (since I typically do not use A/C on an average day).

YMMV

“Get off my lawn you crazy kids!” ?

 

[timbop]

I think what it comes down to is speed limit + whatever minimum additional speed is necessary to keep from being run over from behind

 

[Marcel]

Hey MME Folks,

This is my first electric car, and so far it's great. Anyway, I'm getting ready to go on a road trip next month was was wondering if there is a particular speed that maximizes efficiency? Any intel from more experienced electric car folks would be greatly appreciated. Thanks!

For a road trip charging speed is also a big factor, if there are good charging stops it is usually a good idea to drive faster?

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