August 24, 2021
Believe it or not, not all-electric vehicles (EVs) are the same when it comes to how efficiently they convert the electrical energy in their battery pack into miles down the road.
When you talk about fuel economy in a gasoline engine vehicle, everyone knows that you are talking about efficiency. A car that gets more miles per gallon (mpg) is more fuel-efficient than one that gets a lower number. For EVs, instead of mpg, the most common efficiency measurement is kilowatt-hours per hundred miles (kWh/100 miles). You can think of this as similar to gallons per mile in a gas engine car, so a smaller number indicates a more efficient vehicle—getting 30 kWh/100 miles is better than getting 35 kWh/100 miles, for example.
The US Environmental Protection Agency (EPA) tests the fuel efficiency of gasoline engine vehicles and the energy efficiency of EVs and reports these values to the public. In the EPA tests, a fully charged vehicle is driven on a dynamometer over successive simulated city and highway routes until the battery is depleted. This data also provides the EV’s range reported by the EPA, after the numbers have been subjected to a correction factor to bring it closer to real-world range results. Once a vehicle battery is fully discharged, it is recharged using the manufacturer-supplied charger for that vehicle. The energy consumption is then calculated from the recharging energy, the energy-discharge data from the vehicle, and the distance traveled for each cycle. The recharge energy includes any charging losses due to inefficiencies in the manufacturer’s charger.
There are a variety of reasons why one EV might have greater efficiency than another. The more a vehicle weighs, the greater the amount of energy needed to propel it along the road. To build EVs with greater range, manufacturers are installing larger batteries, which weigh more and make the vehicle less efficient. How easily a vehicle moves through the air (its aerodynamic efficiency) also affects energy consumption. In addition, the way a battery is installed and wired, the efficiency of the power electronics and electric motor, and any other electronic components and accessories all take away power that could have been used to add miles per kWh used.
We looked at the eight worst EVs available (2021 and 2022 models) on the US market and ranked their consumption (in kWh/100 miles) from the worst (49 kWh/100 miles) to the best (35 kWh/100 miles). It’s probably not a surprise that these electron-guzzlers are luxury, performance, and sport models with big batteries that produce long-range capability.
First up, with the worst energy efficiency, is the Porsche Taycan 4S, sport model.
Kevin Clemens is a Senior Editor with Battery Technology.
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