What is MPGe and How is it Calculated?

MPGe (miles per gallon equivalent) is a metric used by the Environmental Protection Agency (EPA) to determine the fuel economy of electric and plug-in hybrid vehicles. It allows consumers to compare energy consumption across electric, hybrid, and gasoline-only vehicles. But how exactly is MPGe determined and what factors go into the calculation? This guide explains MPGe in detail and how it relates to miles per gallon (MPG).

What is MPGe?

How MPGe Measures Electric Vehicle Efficiency

MPGe measures how far a vehicle can travel electrically on the same amount of energy as contained in a gallon of gasoline. While gasoline vehicles use MPG to measure efficiency, MPGe allows for an apples-to-apples comparison with electric vehicles.

For example, a gasoline car that gets 30 MPG and an electric car with a 100 MPGe rating can both travel 30 miles on the same amount of energy - the gas car uses 1 gallon of gasoline, while the electric car uses the amount of electricity equal to a gallon's worth of energy.

The Formula for Calculating MPGe

The MPGe formula uses the EPA energy consumption ratings of a vehicle in kilowatt-hours per 100 miles (kWh/100 mi). It converts the electrical energy consumption to an equivalent number of miles traveled per gallon of gasoline.

The formula is:

MPGe = 33.7 kWh/100 mi ÷ Electricity Consumption Rate (kWh/100 mi)

Where:

• 33.7 kWh = Energy content of one gallon of gasoline
• Electricity Consumption Rate = EPA rating of kWh used per 100 miles

For example:

A vehicle that uses 25 kWh/100 mi would have an MPGe of:

33.7 kWh/100 mi ÷ 25 kWh/100 mi = 134.8 MPGe

So this vehicle can travel 134.8 miles on the amount of electrical energy equivalent to the energy in 1 gallon of gasoline.

Understanding MPG

What Factors Affect MPGe?

The main factors that influence an electric vehicle's MPGe rating are:

• Battery size - Larger battery packs can store more energy for longer electric ranges.
• Weight - Heavier vehicles require more power to accelerate and move.
• Aerodynamics - Sleek shapes that cut through the air efficiently boost MPGe.
• Auxiliary Loads - Features like heat and A/C require extra electrical energy.
• Driving Habits - Aggressive acceleration and high speeds reduce MPGe.

MPGe vs. MPG for Gas Vehicles

Since MPGe converts electrical energy into a gasoline equivalent, it cannot be directly compared to MPG for gas-powered vehicles. The MPG rating for gasoline cars measures how many actual miles can be traveled on one gallon of gasoline.

For example, a gas car that gets 30 MPG will travel 30 miles with 1 gallon of gas. An electric car with a 100 MPGe rating does NOT travel 100 miles on 1 gallon of gas. It travels 100 miles on the amount of electricity equal to the energy in 1 gallon of gas.

So while MPGe is useful for energy comparisons across vehicle types, it does not reflect actual miles per gallon for electric vehicles. The electrical energy consumption rating of kWh/100 mi is a more accurate reflection of how far an EV can travel on electricity alone.

EV Efficiency Comparison Example

Vehicle	MPG (Gas)	MPGe (Electric)	kWh/100mi
Toyota Camry	31	N/A	N/A
Tesla Model 3	N/A	142	24

• The Camry with 31 MPG can travel 31 miles on 1 gallon of gas.
• The Tesla with 142 MPGe can travel 142 miles on the amount of electricity equal to 1 gallon of gas.
• But the Tesla can actually travel 24 kWh/100mi as per its electrical rating.

So while the MPGe rating allows an efficiency comparison, it does not reflect the Tesla's actual electrical mileage.

MPGe Ratings of Popular Electric Vehicles

Here are the MPGe ratings of some popular electric vehicle models:

• Tesla Model S: 120 MPGe
• Nissan Leaf: 118 MPGe
• Tesla Model 3: 142 MPGe
• Chevrolet Bolt: 120 MPGe
• Ford Mustang Mach E: 105 MPGe
• Audi e-tron: 78 MPGe
• Porsche Taycan: 69 MPGe

Generally, battery electric vehicles (BEVs) like the Tesla Model 3 and Chevy Bolt achieve higher MPGe ratings than plug-in hybrids like the Ford Escape and Prius Prime. This is because BEVs rely completely on battery power, while hybrids use both gasoline and electricity.

The MPGe allows quick comparisons across models to determine the most energy efficient options. But be sure to also look at the kWh/100mi rating to understand actual electrical consumption.

Highest and Lowest MPGe Vehicles

Highest MPGe Vehicles

• Hyundai Ioniq Electric: 136 MPGe
• Kia Soul EV: 112 MPGe
• Tesla Model 3 (base): 142 MPGe

Lowest MPGe Vehicles

• Toyota Prius Plug-in: 55 MPGe
• Mini Countryman Plug-in: 57 MPGe
• Audi A3 e-tron: 83 MPGe

Does MPGe Accurately Reflect EV Efficiency?

While MPGe provides a gasoline equivalent metric for electric vehicles, it has some limitations:

• MPGe only considers electrical efficiency - it does not account for differences in gasoline engines.
• It can overstate efficiency compared to real-world conditions.
• MPGe does not factor driving habits, climate conditions, battery degradation over time.
• Ratings are from laboratory tests - actual results will vary.

So while MPGe gives a reasonable baseline comparison, actual efficiencies may differ. Real-world factors like speed, climate control usage, cargo/passenger weight, and driving aggressiveness affect EV range. MPGe is best used to compare vehicles under controlled conditions. Looking at kWh/100mi ratings and actual driving range tests gives a more complete efficiency picture.

The Importance of MPGe in Hybrid and Electric Vehicles

Why is MPGe Used Instead of MPG for EVs?

The EPA uses MPGe instead of MPG for electric vehicles because:

• MPG does not account for electrical energy consumption. MPGe allows efficiency comparisons between electric and gasoline vehicles.
• MPG only measures liquid fuel economy. It cannot accurately gauge efficiency of vehicles running on electricity.
• MPGe was introduced when electric vehicles first entered the market. It allowed consumers to understand EV efficiency in terms of familiar gasoline mileage.
• MPGe has now become the standard for EV fuel economy ratings, allowing easy comparisons across all vehicles.
• MPGe equates electrical and gasoline energy consumption. Without it, there would be no apples-to-apples metric between EV and gasoline mileage.

So while MPGe does not translate directly to actual miles per gallon, it serves an important role as a universal efficiency metric across all vehicle types. This allows consumers to quickly compare MPGe just as they would MPG.

How Automakers Can Improve MPGe Ratings

Automakers can optimize their vehicles to achieve higher MPGe ratings through:

• Lower Aerodynamic Drag - Improving coefficient of drag reduces wind resistance and improves efficiency.
• Lower Weight - Using lightweight materials like aluminum and carbon fiber to reduce vehicle mass.
• Regenerative Braking - Capturing kinetic energy while braking to charge the batteries.
• Temperature Optimization - Heating and cooling systems tuned for efficiency.
• Precision Engineering - Reducing frictional losses and drivetrain resistance.
• Driver Aids - Cruise control, eco mode, and torque optimization to maximize efficiency.
• Battery Improvements - Use higher capacity cells and advanced cooling systems.

Even small design changes can result in measurable MPGe gains. For example, low rolling resistance tires may improve MPGe by 1-2%. Every percentage point counts when aiming for best-in-class ratings.

How to Improve MPGe in Plug-In Hybrids

For plug-in hybrid vehicles (PHEVs) that run on both gasoline and electricity, drivers can optimize MPGe by:

• Minimizing gasoline engine usage - rely more on electric driving.
• Keeping speeds low - higher speeds use more gasoline.
• Avoiding hard accelerations - drive conservatively.
• Charging frequently - keep batteries topped up.
• Preconditioning while plugged in - heat/cool cabin using wall power.
• Using climate control selectively - minimize A/C and heat usage.
• Checking tire pressures - reduce rolling resistance.
• Removing excess cargo weight - lighten the load.
• Upgrading to larger battery - increases electric range.

Properly optimizing electric vs gasoline usage improves PHEV's MPGe rating. Being mindful of driving and charging habits maximizes the MPGe benefit of plug-in hybrids.

The 2023 Chevy Bolt MPGe Rating

The redesigned 2023 Chevy Bolt EV has an EPA-rated MPGe of 118 combined (city/highway 127/108 MPGe). This is up slightly from the previous generation's 116 combined MPGe.

The new Bolt's efficiency improvements include:

• Aerodynamic enhancements like a tapered rear and underbody paneling.
• New low rolling resistance Michelin tires.
• Redesigned driveline with lower friction.
• Regen braking tuned for efficiency.
• Lighter weight materials including aluminum wheels.
• Advanced battery thermal management system.

Together these changes lifted the Bolt's MPGe despite minimal battery pack improvements. With 250 miles of range, the new Bolt achieves excellent electrical efficiency among affordable EVs.

FAQs

Is a higher MPGe rating always better?

Yes, a higher MPGe number generally indicates a more energy efficient electric vehicle. However, MPGe does not consider factors like vehicle size and performance. So larger vehicles with more power may have lower MPGe than compact econo-EVs.

Can MPGe ratings be used to calculate fuel costs?

No, the MPGe rating cannot directly calculate EV energy costs. It only measures efficiency, not electrical energy consumption. To determine costs, you need to look at the kWh/100mi rating and local electricity prices.

Do hybrids have higher MPG or MPGe ratings?

Hybrids that can run on both gasoline and electricity have MPG ratings for gasoline usage and MPGe ratings for electric-only driving. The Toyota Prius Prime has a 54 MPG combined rating and 133 MPGe in EV mode.

What affects real-world MPGe compared to EPA ratings?

Factors like speed, climate settings, terrain, traffic, and driving style can dramatically impact actual MPGe. EPA tests are done in controlled lab conditions. Real-world results vary widely based on conditions.

How often are MPGe ratings updated?

MPGe ratings are adjusted annually as the EPA reviews data and makes changes to testing procedures. Ratings are also updated when automakers make major efficiency improvements during a model year.

Key Takeaways on MPGe

• MPGe allows the efficiency of electric, hybrid, and gasoline cars to be compared.
• MPGe measures how far a vehicle can travel electrically per energy equivalent to 1 gallon of gasoline.
• Higher MPGe ratings indicate greater electrical efficiency, but real-world results vary.
• MPGe does not directly translate to actual miles per gallon for EVs. Look at kWh/100mi for electrical consumption.
• MPGe is useful for comparisons, but has limitations for measuring real-world efficiency.
• Driving conditions, vehicle features, and driving habits significantly impact actual MPGe.

So while MPGe has its shortcomings, it serves as a reasonably effective metric for comparing electric vehicle efficiency on an apples-to-apples basis with conventional gasoline vehicles. As EVs become more prevalent, MPGe provides a useful baseline indicator for consumers assessing their options.

https://wiack.com/research/mpge/?feed_id=493&_unique_id=64c938b92cfec #Wiack