Welcome to SHIFT Basics, a collection of tips, explanations, guides, and advice to keep you up to date on mobility technologies.
Humans have measured gasoline car efficiency in miles per gallon (MPG) and liters per 100 kilometers (L / 100 km) for as long as someone living can remember it.
Both numbers provide drivers with a quick and understandable number that represents the efficiency of their vehicle. For MPG, a higher number is better and for L / 100 km a lower number is better. The more you drive and pay attention to these numbers, the better you will understand what efficiency your vehicle is capable of.
But what about electric vehicles? What numbers do we need to know to understand their efficiency?
When it comes to electric vehicles, we have some metrics that are comparable to the above: MPGe, kWh / 100km, and M / kWh. Let’s take a look at the meaning.
kWh / 100 km
Let’s start with kWh / 100 km. This stands for kilowatt hours per 100 kilometers.
Put simply, this is a measure of how much battery power is used for 100 km. However, it is not a retrospective number. EVs display this number on the dashboard as an indicator of real-time efficiency.
In typical EV range tests, a value between 13 and 20 kWh / 100 km can be considered fairly normal. Smaller and lighter EVs arrive at the lower end of this range, while larger and heavier EVs tend to come out on top.
Some cars give this number in watt hours per km (Wh / km), which is a slightly smaller description of the above values, but means exactly the same thing.
Photo credit: AlexandruAn EV Auto Dashboard Concept. On the right you can see that Wh / km is visible.
If your goal is efficiency, you want this number to be as low as possible.
Kilowatt hours (kWh) are a measure of how much energy is stored. Think of it like an amount of gasoline that is burned every 100 km. When you burn less, you drive more efficiently.[Read: How Netflix shapes mainstream culture, explained by data]
Milers per gallon equivalent, or MPGe, is a little more complicated, but useful when you compare the energy efficiency of an electric vehicle to an old-fashioned gasoline vehicle.
Some clever scientists have managed to calculate how much energy is in a gallon of gasoline and use complex mathematics to show how efficient they are.
These coffins determined that one gallon of gas is equivalent to 33.7 kWh of electrical power. By considering how far an electric vehicle can travel on this amount of electricity, we can calculate a mileage per gallon equivalent to a gasoline vehicle.
Credit: Stanford EduMPGe is used in EPA window stickers on US vehicles to give buyers a number that can be compared to the efficiency of traditional gasoline vehicles.
This is a useful number when you are buying a new car and considering both electric and gasoline vehicles. Most EV drivers, however, prefer kWh / 100 km to measure efficiency in real time. Most EV reviewers put the number per 100km when talking about efficiency rather than MPGe.
Miles per kWh
Another measure of the electrical economy in an electric vehicle is the measure of miles per kWh or M / kWh. In countries where kilometers are the main unit of measurement, this can also be km / kWh.
If you ask me, this is more useful than an MPGe character in the real world. If you drive an electric vehicle, you can see in real time how many kilometers you drive per kWh. If you know how much charge your battery was in kWh before you set off, how long your journey will take and what typical M / kWh your vehicle will hold, you can calculate whether you can charge it without having to get to your destination.
Credit: Wikimedia – CC When looking at the efficiency metrics of your electric vehicle, you won’t get within range and unexpectedly have to go to a charging station.
While driving on the freeway, you can expect an electric vehicle to travel between three and six miles per kWh. Obviously, when using this metric to monitor the efficiency of your vehicle, you would want the count to be higher since, like with MPG, you keep traveling for every unit of energy consumed.
The next time you want to find out how to measure the efficiency of your electric vehicle in the real world, there are at least three metrics you need to use.
If you want to drive as efficiently as possible, you only have a few variables under control. The weight, aerodynamics and drivetrain of your vehicle all affect the efficiency. However, as a driver, you can control tire pressure, how much you accelerate and how fast you drive – all of which affect efficiency.
If you want to convert metrics between these metrics, here’s a handy calculator.
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Published on January 20, 2021 – 13:13 UTC