While an electric vehicle’s range on a charge is arguably its most critical specification – after all, nobody wants to wind up stranded at the side of the road with a depleted battery – its operating efficiency should come in at a close second.

To help consumers compare the energy consumption of electric cars with those that run on fossil fuel, the EPA created a miles-per-gallon equivalent measurement, called “MPGe.” This is calculated based on a conversion factor of 33.705 kilowatt-hours of electricity equaling one gallon of gasoline.

But be aware that the EVs boasting the longest range on a charge are not necessarily the most electricity-efficient. For example, though the new-for-2019 Jaguar i-Pace is rated to run for a stellar 234 miles with a full charge, it’s the least efficient EV among 2019 models in terms of its kilowatt consumption. The Environmental Protection Agency rates the i-Pace at 76 MPGe in combined city/highway driving. While that handily beats any internal combustion vehicle, it trails the electric competition considerably.

The most efficient EV for 2019 is the Hyundai Ioniq Electric, which is rated at a combined 136 MPGe. The EPA says a motorist will spend $1,750 more over a typical five-year ownership period to keep an i-Pace juiced up than will someone driving an Ioniq Electric.

The EPA also expresses an EV’s energy consumption in terms of the number of kilowatt-hours needed to run the vehicle for 100 miles (shortened to “kWh/100 mi”). Also expressed as the abbreviation kWh, kilowatt-hour is a measurement of electrical energy equivalent to a power consumption of 1,000 watts for one hour.

Of course, as is the case with gas-fueled rides, your mileage may vary. That’s because like other vehicle types, EVs are tested for their energy efficiency in a laboratory under controlled conditions and not on the open road. A professional driver runs the vehicle on a dynamometer through multiple standardized driving schedules to simulate city and highway motoring. Once the battery becomes depleted in either cycle, it’s brought back to a full charge and its energy consumption is determined by dividing the kilowatt-hours of energy needed to replenish the battery by the number of miles driven.

Your real-world mileage depends largely on how and where an EV is driven. For starters it won’t match up if you frequently carry a full complement of passengers and/or have a tendency to keep a load of junk in your trunk. All else being equal, the heavier a vehicle’s rolling weight, the more energy is needed to reach and maintain a given speed.

Also, aggressive off-the-line acceleration and driving at higher speeds will tend to consume more electricity. That’s why most EVs earn a higher MPGe rating in city driving, as opposed to highway operation. Also, using a car’s accessories – especially the climate control – and driving on under-inflated tires will also adversely affect an EV’s efficiency.

5. VOLKSWAGEN EGOLF

The full-electric Volkswagen eGolf is rated at 126/111-MPGe (28 kWh/100 miles), which the EPA figures will cost an average owner $550 annually to keep charged.

4. CHEVROLET BOLT EV