Methodology, Sources, and Calculations for EVolution

Step 1: Choose Vehicle

This section was created so that users do not need prior knowledge of which EV models are available. If they have an idea of what they are looking for in a car, based on the information provided, they can fill out this section according to their wants and needs.

• EVolution contains information on all models from 2023–2024. More vehicles from 2024 and 2025 will be added as the vehicle models are released. The information used to narrow down the vehicle selection (i.e., type, size, number of seats, and price range) is taken from fueleconomy.gov, afdc.energy.gov, Edmunds, and OEM (Original Engine Manufacturer) websites (e.g., Ford, GMC, Mercedes-Benz, etc.). The low end of the MSRP is used to sort each model into a price range.
• For PHEV and BEV powertrains, the federal tax incentive from the Qualified Plug-In Electric Drive Motor Vehicles section of the IRS code is factored into the price range. This information can be found at irs.gov.

Step 2: Select Models to Compare

This is a follow-up to Step 1, and allows the user to select which vehicles to compare in the rest of the tool. The models that come up in the drop down list are only those that fit all of the criteria selected in Step 1. The information provided for each vehicle’s cylinders, engine, and transmission is taken from the Fuel Economy Guide.

Step 3: Review Fuel Usage Factors

The purpose of Step 3 is to specify factors that affect driving and fuel usage based on the user’s location and driving habits. The default values are explained below, but to obtain the most accurate outcome of fuel usage and cost, users are allowed to change the inputs.

Fuel Prices

• Default gasoline prices are taken from the Energy Information Administration’s (EIA’s) monthly reports for the Midwest District. These prices are updated monthly to reflect the most recent values.
• Default electricity prices are taken from the EIA's electric power monthly report, specific to the state in which the zip code is located. These prices are also updated monthly.

Travel Info

• The default values for daily mileages, daily travel times, average daily speed, and long distance travel were derived from the 2009 National Household Travel Survey daily travel data. They were sorted by each state and population density that corresponds to the county in which the input zip code is located.
• It is assumed that a typical work week for a user with a full-time job consists of driving 5 days a week, 49 weeks per year.
• The annual mileage is calculated from these default values:

  $$Total\ annual\ miles\ = (daily\ mi) * (\frac{days}{week}) * (\frac{weeks}{year}) + long\ distance\ mi$$

• Long-distance driving habits are assumed to take place the majority of time on the highway, so the highway driving percentage is 80% with 20% city driving.

Step 4: Charging your EV

This step was created to teach anyone interested in purchasing an EV about charging, and to gather information about what their charging habits would look like in order to estimate their electricity usage. It is especially important if one of the selected powertrains is a PHEV to know how much of the daily mileage would run on electric. If both powertrains selected are HEVs, then this step does not apply, because HEVs do not need to be plugged in.

Charging at Home

• The default for charging at home and at the workplace is based on the information in Step 3, Travel Info – with days/week and weeks/year matching the previous input of daily driving habits (default is 5 days/week and 49 weeks/year). It is assumed that the car will be parked at home for these nights, so the default charges/day is 1, but can be changed by the user.
• To give users a better idea of when they would need to recharge the selected powertrains based on their daily driving, the amount of driving on electricity in a day for PHEVs or in multiple days for BEVs is given as:

$$time\ driving\ before\ battery\ needs\ recharging = \frac{0.8* rated\ electric\ range}{daily\ miles}$$

• Here we assume that the PHEV electric range will not cover the daily mileage, so the time is presented as a percentage of a day of driving. Most BEV ranges will cover more than 1 day. Instead of a percentage that would be greater than 100%, their time is presented as number of days, assuming the same distance is covered every day.

Public Charging

If the user is planning on charging while at work or any other place outside of the home, this will also be factored into the total cost of electricity. If the box for “Yes” is not checked, then this does not change anything. If “Yes” is checked:

• The workplace/other public charging inputs, days/week, and weeks/year will reflect the same inputs as the home charging in the same step, but can be changed by the user.
• The number for charges/day is set as 1 for the default; however, this does not always mean 1 full charge. For example, if only half of the battery is depleted, then 1 is taken to mean how much of the battery is recharged, or half.

Step 5: Financial Considerations

Incentives

• Federal incentives refer to the tax credits given out under the Qualified Plug-In Electric Drive Motor Vehicles section of the IRS code (IRC 30D). The incentives depend on make, model, and year of the vehicle. More information can be found at irs.gov.
• State incentives (listed in grey box) include tax credits and rebates. This information was summarized from incentives and laws presented at AFDC.gov.

Cumulative Total Cost of Ownership per Year

This chart is similar to the chart found in the Vehicle Cost Calculator tool. There are a few differences, including the first year price and the option of viewing the total cost of ownership without taking out loans.

The following are variable names and their corresponding description for the use of Step 5. Further calculations used to solve for each value are shown in a chart below the main calculations that are put into the graph. Sources are included in the appendix at the bottom of this page.

For the purpose of these calculations, we refer to all gasoline engine models by their powertrain - internal combustion engine, or ICE.

If “Yes” is checked for the vehicle to be financed, the first-year costs include the initial down payment, fuel costs, loan payment, insurance, license and registration, and the tax incentives for BEV and PHEV are factored out. If “No” is checked, then the down payment and loan payment are replaced with the full price of the vehicle.

ICE & HEV first-year cost:

PHEV first-year cost:

BEV first-year cost:

The vehicle is set to be financed for 90% of the initial cost, with a 5-year loan at 6% interest rate. For years 2 through 5, the annual cost of ownership includes the loan payment, insurance, license and registration, with an escalation factor applied to gasoline and electricity prices.

ICE & HEV years 2–5 cost:

PHEV years 2–5 cost:

BEV years 2-5 cost:

For the remaining years, the annual cost is the sum of the upkeep of owning a car: tires, maintenance, insurance, license, registration, and fuel costs. If “No” is checked for the vehicle to be financed, then years 2 through 5 will be the same as the following:

ICE & HEV years 6–15 cost:

PHEV years 6–15 cost:

BEV years 6–15 cost:

The table below shows where each variable comes from and how they are first calculated for use in the equations above.

Step 6: Adding Up the Benefits of an EV

This is the final step for the tool, and it displays the outcome of all the inputs leading up to this. First, the annual gas usage, fuel costs, and GHG emissions are given. Second, to further exemplify how driving an EV can save money, a chart is included showing daily savings from driving an EV compared to a gasoline engine powertrain based on driving speed. In the calculations below, the conventional gasoline vehicle is referred to by the powertrain – internal combustion engine (ICE).

Annual Comparisons

Gasoline usage [gallons] – this is calculated differently depending on the powertrain. The values used in the calculations are from driving factors and miles per gallon equivalent (MPG(ge))(10). Driving factors are calculated from the inputs in Step 3, and MPG(ge) is the rated combined fuel efficiency from the Fuel Economy Guide. Annual miles is based on the daily driving habits, and how many days in a year the user input for their daily mileage to occur.

Fuel Costs (gas and electric) [$] – this is also calculated differently depending on which powertrain, because the different powertrains are fueled by either gas, electric, or both. These calculations include the gas and electric prices from Step 3, total annual mileage and MPG for powertrains running on gasoline, and kWh/100 miles for powertrains running on electricity. kWh/100 miles is taken from fueleconomy.gov.

GHG Emissions [kg] – emissions are counted as the sum of both upstream and tailpipe emissions, listed on fueleconomy.gov. For EVs, total emissions can be found at Beyond Tailpipe Emissions; our tool uses the national average.

Daily Savings from Driving an EV Compared to the ICE (gasoline engine model)

This graph compares the two alternative powertrains to the selected ICE vehicle. The y-axis shows the amount of money saved in a day based on the x-axis, which shows driving speed. The calculations are derived from the hours spent driving in a day, MPG(ge), electric range of EVs, and fuel prices. These are the initial assumptions made:

• All of the above values vary with the percentage of miles in an urban location, from 100% urban to 0% urban.
• All driving in the scenario is occurring between the low-end speed of 100% urban driving at 19.7 MPH, and the high-end speed of 0% urban driving at 57.9 MPH.
• The faster the speed, the less efficient the battery is, and the range is depleted.
• The average travel time per day is from Step 3 – daily travel factors where the default was derived from NHTS2009 data based on state and county population density.

Starting at 100% urban driving, this is decreased by 5% for each point until reaching 0%. The following calculations are made for each point:

City and highway MPG are from the Fuel Economy Guide. For PHEVs and BEVs, the efficiency used is the MPG or MPGge, also from the Fuel Economy Guide. At 100% urban miles, the combined MPG(ge) equals the rated city MPG(ge), and at 0% urban miles, the combined MPG(ge) equals the rated highway MPG(ge).

For PHEV and BEV powertrains, the kWh/100 miles is set based on the above calculated MPG and their Fuel Economy rated values. This is used to estimate the amount of kWh used in a day.

For PHEVs, the electric range is also necessary to determine how much driving is spent on electric compared to gasoline, with both contributing to the cost of driving.

Next, gallons or kWh by day are computed using the above values and the daily driving time (in hours per day). This is done differently for each powertrain. The miles driven/day equation below affects the PHEV fuel used.

Gallons and kWh are converted into dollars with the price of gasoline and residential electricity in Step 3 – which is then translated into savings when the amount from the EV powertrain is subtracted from the ICE amount.

To make it relevant to the user’s location, the graph also shows the average speed for their location, taken from Step 3. The default value for this is derived from NHTS09, but users could also have changed this during Step 3.

Facts at a Glance:

• Helpful numbers that a consumer might be shown when shopping for a new vehicle.
• For each model, the MSRP, MPG(ge) city/highway/combined, and kWh/100 miles are given.
• These values are from fueleconomy.gov, and where fueleconomy.gov could not provide information, Edmunds was used. The low-end MSRP is shown, which usually represents the basic trim of the model.

Outcome of Adding Up Benefits:

• Given as an overall summary to the tool
• The vehicle with the best fuel efficiency is determined as the vehicle with the highest MPG(ge).
• The vehicle with the most savings is determined as the vehicle with the lowest annual fuel costs; this corresponds to the bar chart at the top of Step 6.
• The vehicle that is best for the environment is determined as the vehicle with the lowest annual GHG emissions, also corresponding to the bar chart at the top of the page.

Appendix

The following table lists the sources of information in the table found in Step 5.