3 ms·

I think it'd be incredibly valuable if all vehicles could pick one common unit. Personally I think that need dominates all others. And it suggests to me MPGe is

I think it'd be incredibly valuable if all vehicles could pick one common unit. Personally I think that need dominates all others. And it suggests to me MPGe is the way to go in the states, to the extend that it makes me want EV "fuel" gauges to be "gallon-equivalents" (33.7kWh). Yes your car only has 2~3 gallons of gas capacity, that's because it's badass & efficient. This is of course (imo: alas) never going to happen. I think the actual units used in EU are, for example, 19kWh/100km (from the BMW iX which does very well for it's size-class). You seem to have an extra /h in your figure. It has the advantage of being a understandable number, relatively well sized in scope. People can think of 100km as a reasonable length in their head that connects distant points. We tend to think in terms of kWh, which is what electricity is typically metered in world wide. It feels like a poor use of a metric system that shouldn't have a bunch of weird prefixes (there's a k above & below the divisor? are you kidding me? 100km? c'mon!!) but the units are people-sized, are things we can work with in our head. And the final number, 19, as in 19 kWh/100km, is reasonably scoped, going up if you're more efficient, going down if you're less efficient. It's inverse from MPG, putting the range-unit is on the bottom & the energy-unit is on the top. Some people love it: they claim that the difference between like 12 & 24 MPG is hard to appreciate the savings off of, whereas the difference between 24 & 48 MPG looks big but is actually only half as much fuel saved. Personally, I don't really chalk this up as a win, but some people think it's important & I can recognize that potentially it might be helpful. I still think we should just use 33.7kWh / 1 gallon-of-gas equivalent as the common unit of energy & give everyone a common frame of reference.

vegardx 4y ago
Some German cars display current usage as kWh/h, which is just a stupid way of saying kW. If you're using 3kW for one hour, that means you're using 3kWh ... per hour. It just doesn't make any sense to write it like that. They correctly display the average usage over a given distance as kWh/100km. There's a lot of fuzz in the EV space since everyone is advertising WLTP (previously NADC) numbers as an indicator for range. It uses a standardized test, so this means the numbers should be comparable. But they're not. Some BEVs are much more efficient in cold weather than others, due to things like heat pumps or just better engineering, like aerodynamics. This isn't well reflected in WLTP, and people get disappointed. You can easily argue for both kWh or Wh. I've always been a proponent of using the smallest units possible, since then everything is just addition, regardless of what you want. With everything being in units of 10, it's fairly easy to do, either way. You could argue that the logical conclusion would be to use Ws/m, which is just ... Joules/m, another SI unit. But then we're using units that most people have no fundamental understanding of.

vegardx 4y ago

Some German cars display current usage as kWh/h, which is just a stupid way of saying kW. If you're using 3kW for one hour, that means you're using 3kWh ... per hour. It just doesn't make any sense to write it like that. They correctly display the average usage over a given distance as kWh/100km. There's a lot of fuzz in the EV space since everyone is advertising WLTP (previously NADC) numbers as an indicator for range. It uses a standardized test, so this means the numbers should be comparable. But they're not. Some BEVs are much more efficient in cold weather than others, due to things like heat pumps or just better engineering, like aerodynamics. This isn't well reflected in WLTP, and people get disappointed. You can easily argue for both kWh or Wh. I've always been a proponent of using the smallest units possible, since then everything is just addition, regardless of what you want. With everything being in units of 10, it's fairly easy to do, either way. You could argue that the logical conclusion would be to use Ws/m, which is just ... Joules/m, another SI unit. But then we're using units that most people have no fundamental understanding of.