MPGe Meaning Explained: Efficiency Ratings For PHEVs And EVs

A major factor in comparing potential new car options today is assessing overall efficiency, known as a vehicle’s average miles per gallon, or MPG rating. For vehicles that utilize a plug-in hybrid system (also known as PHEVs) or an all-electric powertrain, a different grade of average energy efficiency can also apply, known as MPGe. For new car buyers, there may be some confusion as to what sets apart MPGe from normal MPG ratings, and why it matters for vehicles like the Tesla Cybertruck. Along with the MPGe metric’s meaning, we’ll explain why it may not be the best way to measure an EV’s efficiency.

What Does MPGe Mean?

MPGe is an abbreviation for ‘miles per gallon equivalent’, serving as an industry-standardized way of measuring the efficiency of alternatively fueled vehicles – ranging from hydrogen models to PHEVs and all-electric cars. Since these cars rely partially or fully on electric power, the traditional mpg rating – based on how far a gas-powered car can travel on a gallon of gas – couldn’t be used. It’s the “equivalent” part of the MPGe metric that’s most important, since this measurement converts the energy consumption of these electrified vehicles into the equivalent miles a normal ICE model would travel on a gallon of fuel.

This designation was introduced by the United States Environment Protection Agency (EPA) in 2010 as cars like the all-electric Nissan Leaf and plug-in hybrid Chevrolet Volt entered the market. MPGe ratings would eventually be added to the window stickers, or Monroney Labels, of new cars sold from 2012 onwards, before the ratings themselves became mandatory with any new car sold in North America. The intention of including these ratings on the labels is to offer as much realistic transparency about any given partial or non-internal combustion-powered vehicle’s energy efficiency.

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Why Do PHEVs Have Both MPGe and MPG Ratings?

PHEV models sold in North America are given both an MPGe and MPG rating by the EPA. This is because vehicles utilizing this powertrain are not just limited to using gasoline or electricity as a primary energy source – they can use one or the other, or both in unison.

Therefore, when looking up fuel economy figures for PHEVs, some models will give separate figures:

• 2025 Kia Niro Plug-In Hybrid EPA-estimated combined gas and electric rating: 108 MPGe
• 2025 Kia Niro Plug-In Hybrid EPA-estimated gasoline-only rating: 48 mpg

Providing both ratings allows the EPA to be as accurate and transparent as possible when depicting the efficiency of a new model, getting a realistic idea of what mileage the vehicle can achieve using both gas and electric power, while also being able to refer to the traditional mpg rating when it runs only on gasoline.

MPG Vs. MPGe

Though some may assume there is a big difference between MPGe vs MPG as a rating system, the truth is that little separates these two systems apart as a method to assess overall efficiency between vehicle models. Though, as their name suggests, MPG applies primarily to full-gasoline vehicles. When buyers first get details about a new PHEV, the MPGe figure is pushed to be the more prevalent number on the window sticker or sales brief – the gasoline-only MPG rating is still included among all the other key information included about the model, though in a much smaller font.

As EVs contain no internal combustion powertrain within their design, they are only designated an MPGe rating on their window sticker.

Essentially, the only vehicles with an MPG rating alone are exclusively gas-powered models, or those that typically can’t run on electric power alone, such as mild hybrids and conventional hybrids. PHEVs and EVs, however, will receive an MPGe rating.

Are MPGe Ratings Accurate?

To gauge whether MPGe figures are an accurate representation of a PHEV or EV’s true efficiency, we need to first understand how an MPGe rating is calculated. Currently, the EPA treats a single gallon of gas as the equivalent amount of 33.7 kWh of energy.

Some may know that the MPG ratings for full gasoline cars do not always reflect what they are capable of in the real world, especially given other factors like weather, driving style, and tires, all of which are not factored into the controlled environment by which their MPG ratings are calculated. MPGe ratings are also subject to this issue. This is largely due to the method by which MPGe ratings are calculated, which are done in controlled environments that may not provide an accurate representation of what a PHEV or EV may experience when out on public roads.

Furthermore, when assessing electric vehicles, the there is a sense that MPGe is not the most ideal metric to gauge their overall efficiency. Some are pointing towards other methods, such as measuring how many miles an EV can reach per kilowatt-hour – also known as mi/kWh, this offers a more realistic and easier way to accurately rank an EV’s efficiency performance with their use of electric charge in real time, even if it’s an estimate of average consumption.

Where the MPGe rating does help is when comparing the efficiency ratings of EVs or PHEVs with traditional, gas-powered vehicles. A combination of MPGe and mi/kWh ratings would be the most helpful way to determine the efficiency of EVs and PHEVs.

What Is Considered A Good MPGe Rating?

Similar to interpreting what a good or above-average MPG rating implies on the fuel economy of an ICE vehicle, there are also some EVs and PHEVs that are especially efficient. Most buyers immediately know that an SUV hitting over 35 mpg is efficient, but it’s less obvious what number to look out for in terms of MPGe. The below models can help to keep running costs down, but bear in mind that an efficient EV does not automatically equal an EV with a long range on a charge. The size of an EV’s battery and the weight or design of that car heavily impacts range.

Below are a few examples of vehicles that deliver great MPGe ratings within their respective segments.

*combined

These models should be compared with their direct class rivals, not each other, to determine efficiency. For example, the Model Y’s 125 MPGe is quite a bit better than the best the Ford Mustang Mach-E (106 MPGe) can achieve. At 88 MPGe, meanwhile, the BMW i7 gets nowhere close to the Lucid Air’s 146 MPGe, yet both are large and luxurious electric sedans.

Why Is It Hard To Match EPA Ratings For MPGe?

While MPGe ratings are a valuable reference point in comparing options based on efficiency, as mentioned above, these numbers may not accurately represent the given car’s true real-world energy consumption. The controlled environment in which the government MPGe ratings are generated means these numbers do not take into account other variables from real-world driving environments, as well as naturally occurring variables unique to the given vehicle and the driver, that can affect the overall efficiency.

Factors Affecting MPGe Ratings

• Driving Style – aggressive, fast driving leads to poorer fuel economy/range.
• Aerodynamics – additional accessories, like roof attachments or external spoilers (functional), can increase or reduce a vehicle’s overall aerodynamic properties. The harder a vehicle has to fight against airflow at speed, the less efficient it is.
• Weather Conditions – colder temperatures can affect battery performance.
• Weight (total number of passengers, cargo load) – a heavier vehicle means it requires more power to move, which in turn can mean poorer efficiency/range.
• Tire Condition – are all four tires inflated to the correct manufacturer specifications? The type of tires installed is also a factor in efficiency, with some providing better rolling resistance than others.
• Wheel and Tire Size – For electric vehicles, the size of tires and wheels are also a contributing factor to the overall estimated range (bigger wheels can translate into less range compared to the same model with smaller ones)
• Use of cabin equipment – turning on interior features like air conditioning, heated steering wheel/windows can drain more energy, especially if they are used for extended periods of time

Considering the MPGe figures for your next PHEV or EV purchase, nonetheless, is a valuable tool among other factors to consider when in the market for one. But you shouldn’t fixate on these numbers alone in your decision of which option to ultimately put your money towards.

Sources: EPA, BMW, Hyundai, Lucid Air, Tesla, Kia, Toyota, Subaru, Genesis, Vinfast, Mitsubishi, Lexus, Volvo, Stellantis, Land Rover, Porsche