Plug-in Hybrid Economy Calculator

Created by Bogna Szyk
Reviewed by Steven Wooding
Last updated: Apr 06, 2022

Most electric and hybrid cars allow you to save considerable sums on fuel but require a significant initial investment. It isn't easy to decide at 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 vehicles.

The main difficulty in determining the PHEV cost-effectiveness is that it is mainly dependent on your driving style. The purchase of such a vehicle is justified if you make a lot of short trips. However, once you deplete the battery and switch to gasoline, 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 make a 400-mile 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 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 vehicles. 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 can use only the battery without drawing any energy from the combustion engine. Once the battery reaches a specific low state of charge, the car switches to gasoline as the primary propulsion method. On short distances, the PHEV will not use gasoline at all – it is used only to extend the battery-only (EV) range of the car.

The other difference between plug-in hybrids and traditional hybrids is that you can recharge the battery in a PHEV from the grid. Most producers provide the 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 braking, 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 find its MPG (miles per gallon) value in the specifications, determine your monthly mileage, and perform a simple division to obtain the fuel cost 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 separately estimate the mileage within and beyond the EV (battery-only) range. Only then can you 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 can 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 by choosing a plug-in hybrid from a range of available models. Our calculator allows you to select one of the models listed in the table below. All data comes from fueleconomy.gov and their 2017 Fuel Economy Guide. You may provide your own values if your vehicle is not on the list.

Model

Battery-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 category.

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 work 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 a PHEV car is calculated using 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 the following formula:

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

where:

  • MPGe — Equivalent fuel efficiency of the PHEV (miles per gallon);
  • s₁ — Total mileage traveled on battery;
  • s₂ — Total mileage traveled on gasoline;
  • EE — Energy efficiency of the battery in kWh per 100 miles; and
  • MPG — 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 electricity per kWh in your area.

When choosing the price of electricity, double-check whether you can use a tariff with a variable cost 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 made 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 based 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 the investment will 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 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
mi
Car cost
$
Consumption rate
kWh/100
mi
MPG (gas only)
US mpg
Trips shorter than battery range
Average distance travelled
mi
Trips per month
Trips longer than battery range
Average distance travelled
mi
Trips per month
Real-life MPG
Distance on battery
mi
Distance on gas
mi
Your MPG
US mpg
Monthly expenses
Gas price
$/
US gal
Electricity price
$/
kWh
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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