Most electric and hybrid cars allow you to save considerable sums on fuel but require a large initial investment. It is difficult to decide at the first glance whether a hybrid is more cost-efficient. We created this handy calculator to give you a comprehensive overview of the economy of plug-in hybrids. You will be able to calculate the real-life MPG of such a car and compare the energy expenses of plug-in hybrids and regular cars.

The main difficulty in determining the PHEV cost-effectiveness is that it is largely dependent on your driving style. The purchase of such a vehicle is justified if you make a lot of short trips. Once you deplete the battery and switch to gasoline, though, it is only as good as a regular car.

To calculate the MPG of your PHEV, determine how many trips you make within and beyond the battery-only (EV) range. For example, if your only trips during the month are for commuting - let's say, 15 miles on every workday - then you can assess your monthly mileage as 20 * 15 miles. Estimate how many long-distance trips you make each month, too; for instance, you can make a 400-miles journey twice a month to visit your parents.

As our calculator already aggregates the most important data concerning energy consumption of plug-in hybrids, there's no need for you to do a thorough research. All you have to do is choose a car from the list, and our calculator will tell you how much you will save on fuel.

What are the plug-in hybrids?

Plug-in hybrid electric vehicles (PHEV) are cars that use two propulsion methods. The first is an internal combustion engine, fueled with gasoline, just like in traditional cars. The second is an electric motor with a rechargeable battery.

Unlike regular hybrid vehicles (HEV), plug-in hybrids operate primarily on the electric motor. They are able to use only the battery without drawing any energy from the combustion engine. Once the battery reaches a certain low state of charge, the car switches to gasoline as the main propulsion method. On short distances, the PHEV will not use the gasoline at all - it is used only to extend the battery-only (EV) range of the car.

The further difference between plug-in hybrids and traditional hybrids is that the battery in PHEV can be recharged from the grid. Most producers provide a possibility to charge the car from a standard plug socket. You can also use dedicated charging stations. The batteries of HEV are typically recharged on board, for example during regenerative breaking, when kinetic energy is recaptured.

What does our calculator do?

Estimating the fuel costs of a regular car is not a difficult task. All you have to do is to find its MPG (miles per gallon) value in the specifications, determine your monthly mileage, and perform a simple division to obtain the cost of fuel per month.

The calculations become more daunting when you are trying to find the energy costs of a PHEV. As it switches between two propulsion methods, you have to estimate the mileage within and beyond the EV (battery-only) range separately. Only then you can find the real-life MPG of the plug-in hybrid that will correspond to your driving style.

Intuitively, the plug-in hybrids are the best solution for drivers who primarily operate on short distances. They are able to charge their car's battery frequently and spend months without burning fuel. On the other hand, a driver who often makes long trips will quickly discover that the real-life MPG of his plug-in hybrid does not differ much from the MPG of a car not equipped with an electric motor.

Plug-in hybrid car models

Begin your analysis with choosing a plug-in hybrid from a range of available models. Our calculator allows you to choose one of the models listed in the table below. All data comes from and from their 2017 Fuel Economy Guide. You may provide your own values if your vehicle is not on the list.

modelbattery-only range (miles)MPG (if operating on gas only)car price (US $)kWh / 100 miles (if operating on battery only)
Audi A3 E-Tron 16 34 38,900 41
BMW 330e 22 31 43,700 47
BMW 740e 14 27 89,100 52
BMW i8 15 28 137,000 43
BMW X5 xdrive40e 13 24 64,000 59
Chevrolet Volt 53 37 34,000 31
Chrysler Pacifica Plug-in Hybrid 30 32 43,100 40
Ford C-Max Energi 19 38 32,600 35
Ford Fusion Energi 21 38 33,900 35
Hyundai Sonata Plug-in Hybrid 27 40 35,400 34
Kia Optima PHEV 29 40 35,210 33
Mercedes C350e 20 30 46,400 56
Mercedes S550e 20 26 95,650 59
Mercedes-Benz GLE550e 19 21 67,000 69
Mitsubishi Outlander PHEV 32 51.4 41,600 31
Porsche Cayenne S E-Hybrid 14 22 78,000 71
Porsche Panamera S E-Hybrid 16 25 93,000 52
Porsche 918 Spyder 12 22 845,000 50
Toyota Prius Prime 25 54 27,100 25
Volvo XC90 T8 17 22.5 69,000 60

Calculating the real-life MPG

The next step in calculating the MPG of your plug-in hybrid is to analyze your driving habits. Divide all the car trips you make during a month into ones that do and do not exceed the car's EV range. You need to provide our calculator with the average distance of a trip and the number of trips per month for each of these categories.

Our plug-in hybrid economy calculator assumes that the car operates either on battery only, or - when the battery is depleted - on gasoline only. It is a necessary simplification, as many vehicles can also operate in a so-called "blended mode", where the two propulsion methods are applied simultaneously. Nevertheless, it is a good approximation, especially for drivers who make most of their trips within the EV range.

The fuel efficiency of PHEV car is calculated with the use of miles per gallon gasoline equivalent (MPGe). According to the Environmental Protection Agency, one gallon of gasoline corresponds to 33.7 kWh of electric energy. Thus, your real-life MPG is calculated with to the following formula:

MPGe = (s₁ + s₂) / (s₁ * EE / 3370 + s₂ / MPG)


  • MPGe stands for the equivalent fuel efficiency of the PHEV (miles per gallon),
  • s₁ is the total mileage traveled on battery,
  • s₂ is the total mileage traveled on gasoline,
  • EE is the energy efficiency of the battery in kWh per 100 miles,
  • MPG is the fuel efficiency of the PHEV operating on gasoline only.

Costs of use

Apart from the MPG of a plug-in hybrid, our calculator can also determine your expenses on gas and electricity. All you have to do is provide the price of fuel per gallon and of electricity per kWh in your area.

When choosing the price of electricity, double-check whether you can use a tariff with a variable price per kWh depending on the time of the day (tiered electricity pricing). If so, you can open the advanced mode to type in two different electricity prices. You can assign a different percentage of total charging time to each of them. You can also use these fields if, for example, you charge your car for free at your workplace. Then, simply set the tier 2 electricity price to $0/kWh.

Our calculator will automatically display the total monthly cost of using a plug-in hybrid. You can also open the advanced mode to see the cost split into the gasoline and electricity parts.

Comparison with a regular car

Now that you know your monthly energy expenses, you can compare the selected plug-in hybrid vehicle with any regular car that operates solely on a combustion engine. All you have to do is to find the MPG of this car on its producer's website. Choose the value that best corresponds to your driving habits - for example, if you only use your car in the city at low velocities, choose the "city fuel economy" type. On the other hand, if most of your trips are done at high speeds, "highway fuel economy" will be more suitable.

Upon entering the MPG of the traditional car, our calculator will automatically determine the fuel costs basing on your driving habits and monthly mileage. It will also display how much money you will save each month if you settle for a PHEV instead.

Should you buy a PHEV?

Every plug-in hybrid vehicle will be cheaper than a regular car when it comes to fuel and energy expenses. It doesn't necessarily mean, though, that the sum you have to invest will return to you.

When you open the advanced mode of our calculator, you will discover an additional section at the very bottom. You need to enter the price of a regular car and the price of a charging station, if you wish to install one at your own house (if you already have a station or don't want one, type "0" into this box). Also, input the value of the government incentive/grant (if you receive any). Then, the calculator will compare the costs of PHEV and the regular car and tell you after how many years will the investment be returned.

Remember that the economic factor should not be the only one that influences your decision. For example, hybrid cars are far more sustainable than the regular ones. Also, make sure to consider other expenses and savings such as:

  • Toll exemptions: In many countries, PHEV or HEV owners can use the highways without paying the toll.
  • Insurance and maintenance: The rates may be different for hybrid and regular cars.
Bogna Szyk
Car model
Car model
Toyota Prius Prime
Range on battery
Car cost
Consumption rate
MPG (gas only)
US mpg
Trips shorter than battery range
Average distance travelled
Trips per month
Trips longer than battery range
Average distance travelled
Trips per month
Real-life MPG
Distance on battery
Distance on gas
Your MPG
US mpg
Monthly expenses
Gas price
US gal
Electricity price
Total energy costs
per month
Comparison with a regular car
MPG of a regular car
US mpg
Expenses (gas)
per month
PHEV savings
per month
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