What is the Equivalent of MPG for an EV?
One of the most common questions when buying or leasing a car is “what’s the MPG?” Fuel economy directly impacts one of the most considerable running costs of an internal combustion engine (ICE) vehicle. Knowing how many miles per gallon you’ll get can help decide what make and model to drive.
For obvious reasons, electric vehicles are different. They don’t have liquid fuel, so there is no MPG to compare. And yet, the electricity you use to recharge the battery costs money, so there is an equivalent to traditional ‘fuel economy’.
So, what is the equivalent of MPG for an EV, and what will affect the cost of each mile you drive? Let’s take a look…
Fuel Economy of EVs
It’s not too difficult to understand how the fuel economy of EVs is measured. On an ICE vehicle, a gallon is the standard measure of a unit of fuel – at least for calculating fuel economy.
The standard unit of energy on an electric vehicle is a kilowatt-hour, abbreviated to kWh. Therefore, you’ll often see EV fuel economy listed as miles per kWh (or kilometres per kWh in countries that use the metric system for road distances).
A measure of fuel economy in terms of kWh is handy for EVs, as it simplifies the calculation when recharging your vehicle – multiply the price per kWh by the fuel economy, and you’ll have a good idea of the total cost of electricity for your journey.
Comparing the Fuel Economy of EVs and ICEs
One problem with these different types of fuel economy is that it can be hard to compare EVs and ICEs to determine which is cheaper to run (although it’s highly likely that an EV will be significantly cheaper than its ICE equivalent).
To overcome this problem, manufacturers developed the concept of MPGe, or Miles Per Gallon equivalent. It just so happens that the acronym works equally well for ‘Miles Per Gallon electric’ if you prefer to think of it that way.
In creating this unit, the US Environmental Protection Agency used British Thermal Units (BTUs), the amount of heat generated by burning a quantity of fuel. The total thermal energy generated during combustion is 115,000 BTUs for a gallon of gasoline.
To get the same amount of energy from a battery, you need 33.7 kWh of charge – so fuel efficiency in MPGe is the distance an EV can cover using 33.7 kWh of energy.
What Affects the Fuel Economy of EVs?
Some of the newest electric car models have highly efficient batteries with record-breaking capacity, allowing them to cover much longer distances on a single charge.
Higher capacity alone does not mean better fuel economy – in ICE terms; capacity is the size of your fuel tank, not the efficiency of your engine. So a larger battery does not equate to lower running costs.
In contrast, efficient motors that use less electrical power to run will offer better fuel economy (or power economy, if you prefer not to think of electricity as ‘fuel’ in the traditional sense).
It must be noted, however, that manufacturers’ stated electric ranges are dependent on driving conditions and individual driving style.
What Affects the Price Per Mile of an EV?
Fuel efficiency will directly impact the price per mile of any vehicle, whether an ICE or an EV, but it’s not the only factor. The price per unit of fuel is the other part of the calculation, and we all know that for petrol, diesel and gasoline, higher prices at the pump mean journeys cost more.
The same is true of units of electricity. Charge at an ultra-fast commercial charging station, where the price per kWh is highest, and your journeys will cost more (although charging will be much faster). Recharge at home – especially if you’re on a tariff that allows you to pay less per unit by charging overnight – and you can substantially cut the cost of running an electric car.
Running onboard electrical systems like air conditioning can also drain an EV battery faster, reducing the real-term fuel efficiency of the journey. However, this should be a relatively small impact on most modern EVs.
Overall, because of the lower cost of electricity compared with conventional liquid vehicle fuels like petrol and gasoline, the actual price you pay for a journey by EV is likely to be much lower than in an ICE. But fuel economy – or power efficiency – is still a great tool when narrowing down a shortlist of EVs to buy or lease.
