Understanding "Average" efficiently

I picked up a 2015 SL a few months back, and I'm loving it. A fantastic way to bomb around the city and do my 15 minute "commute" M-F.

I was just watching Fully Charged Show, Jack is looking at a super efficient experimental Mercedes. When he gets to the numbers he says it runs 7kWh per 100km. Here's where I'm confused - there's an efficiency display on the Leaf, and mine currently reads 6.4, the car is set to metric, so I had assumed that was 6.4kWh per 100km. So, either the display in front of me on the Leaf is not kWh per 100km, or I don't understand how that measurement works, wouldn't using fewer kWh per 100km be more efficient?

https://www.youtube.com/watch?v=BS1SBhBjAHY

Welcome. He may have misspoken, or you may have misheard him. It's supposed to be KM per KWH, not the other way round. Because, as you noted, bigger efficiency numbers should be better, not worse, than smaller ones.

7 km/kWh seems about right but that is roughly 4.3 mi/kWh, which is slightly less than my normal efficiency in my 2017 Leaf S.

I didn't watch the video so maybe this spec was for an average speed of 75mph or something but otherwise, it is either just hype or completely wrong.

7 kWh / 100 km would be equal to 14.3 km / kWh or 8.8 mi / kWh. That would indeed be amazing efficiency but somehow it's hard to believe today's tech can achieve that in normal conditions.

OK, I think the "6.4" number my Leaf is showing me must be in a different scale than what is being used in that video. Looking in the US owners manual the economy screen is in Miles/kWh like LeftieBiker & Goldbrick say. Mine will be the metric version of that I expect, so 6.4 km/kWh (guess I must have a lead foot )

6.4 km/kWh = 15.53kWh/100km

So, ya, 7kWh per 100km is crazy good economy. That makes sense now

I just watched the first part and it is supposedly 8.7 kWh / 100 km or about 7.1 mi / kWh. That's great efficiency!

There is also no active cooling. I have no idea what kind of chemistry is used for the battery but it is interesting that MB thinks there is at least some chance that the battery doesn't need any external cooling. It is a 'concept' car but that's a big thing to retro-fit.

MeatBreadMeat said:

I picked up a 2015 SL a few months back, and I'm loving it. A fantastic way to bomb around the city and do my 15 minute "commute" M-F.

I was just watching Fully Charged Show, Jack is looking at a super efficient experimental Mercedes. When he gets to the numbers he says it runs 7kWh per 100km. Here's where I'm confused - there's an efficiency display on the Leaf, and mine currently reads 6.4, the car is set to metric, so I had assumed that was 6.4kWh per 100km. So, either the display in front of me on the Leaf is not kWh per 100km, or I don't understand how that measurement works, wouldn't using fewer kWh per 100km be more efficient?

Click to expand...

I think in the UK where the show is produced, it's more common for people to state "fuel economy" in terms of liters of fuel consumed per 100km. The habit seems to have carried forward to EV economy as well, simply substituting kWh.