Abstract
Internal combustion engine vehicles have long dominated personal vehicle sales in the United States. As electric vehicles gain market share, understanding fuel costs of gasoline versus electric vehicles (EVs) is increasingly relevant for potential buyers and for researchers. In particular, understanding the influence of fuel price volatility on fuel costs is of interest. Although it is well known that fueling an EV is cheaper than fueling a gasoline vehicle, costs are less commonly expressed in explicit spatially and temporally resolved terms. This note presents an Excel model that includes state-specific gasoline and residential electricity price data for US states between 2015–2020, including both average overall electricity prices and lowest-cost time-of-use electricity rates (measured over a consecutive 8-hour potential residential charging period) for each state. This model, which we call the Fuel Cost Calculator, also allows users to evaluate the impact of several major external and driver behavior factors on fuel costs for gasoline versus electric vehicles. These combinations of these factors result in unique scenarios which make price differences for the fuel costs more variable. With the Fuel Cost Calculator, the user can create specific scenarios reflecting potential real-world conditions to create cost estimates for gasoline and residential EV fueling over user-determined time periods and distances. Fuel costs for gasoline vehicles are generally higher than for electric vehicles in the US, consistent with prior studies. We also explicitly show that fuel cost budgets are much more volatile for gasoline versus electric vehicles charged at a residence, given the much less stable price of oil versus electricity. This volatility is sufficiently large so as to be relevant for vehicle owner budgets. The FCC also shows carbon dioxide (CO2) emissions associated with vehicle use, resolved at the state level.
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Nomenclature
| EV | electric vehicle |
| FCC | Fuel Cost Calculator |
| GHG | greenhouse gas |
| ICEV | internal combustion engine vehicle |
| kWh | kilowatt hour |
| MPG | miles per gallon |
| MPGe | miles per gallon equivalent |
| TCO | total cost of ownership |
| TOU | time-of-use |
| US | United States |
1. Introduction
Today, there are roughly one million personal automobile EVs on the road in the US. By 2030, this number is expected to reach almost 20 million, which would account for about 7% of vehicles on the road [1]. Many vehicle manufacturers have already made plans to slow down or completely stop their production of ICEVs in the future. For example, General Motors plans to end the sale of gasoline and diesel engine vehicles by 2035 [2], and Volkswagen plans to have half of its US vehicle sales be EVs by 2030 [3]. EVs are rapidly gaining market share and could become the dominant type of vehicles on the road within many of our lifetimes.
EVs are important because of their long term economic and environmental impacts [4]. Decarbonization is one major motivation for vehicle electrification, particularly because EV GHG emissions decline as the grid decarbonizes. Today, EVs are more expensive than ICEVs largely due to their batteries [5]. However, battery prices have fallen rapidly and are expected to continue to fall [6], which could make EVs more affordable and potentially cheaper than standard ICEVs.
As production costs of EVs approach the retail prices of ICEVs, fuel costs become more significant when comparing life cycle costs of EVs and ICEVs. EVs are more energy-efficient since they proportionally convert more energy from electricity to wheel power than ICEVs convert from gasoline. EVs can convert over 75% of the electrical energy they consume to power at the wheels, while ICEVs can only convert 12%–30% of the energy in gasoline [7]. This results in EVs having higher MPGe fuel efficiencies than ICEVs. Since EVs are more energy-efficient, this results in cheaper fuel costs than ICEVs for a given travel distance. However, fuel costs do not influence customers as much as TCO when deciding which vehicle to buy [8]. While some customers may not recognize how fuel cost financially impacts the TCO, fuel costs play a significant role in TCO over the long term [9].
External conditions and driving habits can affect the fuel efficiency of vehicles, with an impact on fuel costs. External conditions include the year, month, state, and temperature. Driving habits are more specific to a given user, such as additional cargo added or the split between highway and city driving. Combinations of all of these factors can create scenarios that are unique to an individual, and can have an impact on the fuel costs associated with driving a certain vehicle type.
One underinvestigated issue related to fuel costs for EVs versus ICEVs is that when EVs are charged with electricity at residential rates, EV fuel costs are not only lower, but also much more predictable than ICEV fuel costs, given that gasoline prices are far more volatile than electricity prices. They tend to fluctuate throughout the year essentially unpredictably, which can make it difficult to budget for ICEV fuel costs. Electricity prices tend to remain stable throughout the year, but general prices can vary depending on what type of payment plan the customer is on. In most states, users can select a TOU electricity rate plan, which provides cheaper electricity rates during certain 'off-peak' hours of the day. If the customer decides to charge their EV during these off-peak hours, they can save even more money on fueling their vehicle. Some utilities even offer plans specifically for electric vehicle owners, which can even further reduce the costs of fueling.
This note introduces a Fuel Cost Calculator (FCC) that compares the costs of gasoline and residential electric vehicle fueling in the US, based on real fuel costs for 2015–2020, included as the Supplementary Information (SI). The remainder of this note describes the FCC and potential applications.
2. Methods
The Fuel Cost Calculator is an Excel workbook that includes a user-manipulable input sheet, historical data, and calculations. For this study, data were collected per state and per year (2015-2020) for average gasoline prices [10], average retail kWh prices [11], and residential TOU rates and utility names [12] if available. Out of the 300 residential TOU rates possible, 95 were not available for a specific state and year and could not be included in the calculator. As the calculator includes example rates by state rather than utility for consistency with available gasoline price data, states with multiple utilities with TOU use rates were assigned the utility and rate with the lowest rate over at least eight consecutive hours of the day, based on an approximation of overnight residential EV charging. These data are included in the SI on the sheet titled 'Data'. Assumptions used in this study are listed in the sheet titled 'Assumptions'. Calculations are performed on a hidden sheet titled 'Calculations.' On the 'Inputs & Outputs' sheet (figure 1), users can adjust assumptions and compare estimated vehicle costs between ICEVs and EVs, but also for selected versus lowest-cost conditions. Users are also able to select metric or US customary units for data display. Although much of the model is locked to prevent accidental overriding of formulas, there is no password.
Figure 1. Fuel Cost Calculator for ICEVs and EVs in the US, User Inputs.
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Standard image High-resolution imageTrends for factors that have an effect on the fuel costs of EVs and ICEVs were also researched and collected. These factors include temperature changes [13–15], cargo added [16], and month [17, 18]. The calculator also includes CO2 emissions factors per gallon of gasoline or per kWh by state, which allows one to see how their driving conditions and vehicle type impact climate change [19, 20]. The FCC prioritized fuel cost drivers that are measurable, have a meaningful impact on fuel efficiencies, and can be approximated relatively easily. There are some factors that have an effect on fuel efficiencies but were excluded because they do not have a consistent, meaningful effect or are hard to approximate. Examples of some excluded factors are rapid acceleration and braking, driving with the windows down, driving with the air conditioning on, and driving on sloped surfaces. While these factors all have effects on fuel efficiencies, they are hard to record and measure and/or would not significantly affect the fuel efficiencies or fuel costs.
Each trend collected is convertible to a percent change in original fuel efficiency, all of which can be summed to create a total percent change in fuel efficiency. This was used to calculate new fuel efficiencies for EVs and ICEVs based on their inputted fuel efficiencies. The new fuel efficiencies and the selected gasoline or electricity price for a given year and state allows for the calculation of fuel cost, given in a price per distance or price per time format.
3. Products
The FCC enables the user to compare fuel costs and GHG impacts of EVs and ICEVs, assuming either residential charging or gasoline fueling, by inputting specific driving conditions.
The required inputs for the FCC are state, year (2015-2020), highway fuel efficiency, and city fuel efficiency. For ICEVs, the user must input fuel efficiency in units of MPG, and for EVs, the user can choose between units of kWh/100 miles, miles/kWh, and MPGe. For EVs, the user is also required to select which electricity price to use, being either the average residential kWh price or the cheapest standard/TOU electricity rate. Optional inputs for the FCC include percentage split between highway and city driving, temperature (°F or °C), additional cargo (pounds or kilograms), distance driven (miles/kilometers per year/month), and month. The outputs of the FCC are fuel cost and CO2 emissions. The user has the option to display fuel cost in cents per mile, cents per kilometer, or dollars per month (only if the user inputted a distance driven). CO2 emissions can be displayed in grams per mile, grams per kilometer, and kilograms per month (only if the user inputted a distance driven). Below the outputs, the FCC will display the ideal conditions for the cheapest fuel cost. Below that, there are waterfall graphs showing the fuel cost under lowest-cost versus input conditions listed and in the units that the user selected (figure 2).
Figure 2. Waterfall graph showing drivers of differences between costs under user input conditions and lowest-cost conditions.
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Standard image High-resolution imageThe extensive historical data for US fuel costs (gasoline and electricity) by state for 2015–2020 also enables users to construct estimates of monthly fuel budgets under various driving conditions. Figure 3 shows an average expected monthly cost as an example.
Figure 3. Graph comparing the volatility of monthly fuel costs for ICEV and EV users in the United States from 2015 to 2020 based on simple average fuel costs across states and default driving assumptions.
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Standard image High-resolution image
4. Discussion
The FCC is an accessible Excel-based tool designed to enable users to easily evaluate the effect of variable fuel pricing on fuel costs for ICEVs and EVs in the United States. The large number of spatially resolved, historical fuel price time series in particular enables deep investigation of potential fuel costs. Researchers studying the effects of specific conditions on the fuel costs of ICEVs and EVs can easily look at real-world historical fuel cost data in the context of conditions they might be studying. Potential vehicle purchasers can use the FCC to evaluate how their needs and behaviors might translate to fuel costs, enabling better budget planning. People preparing to move to another state can compare fuel costs in states side by side for either type of vehicle. Also, users looking to become new vehicle owners can directly compare the fuel costs of ICEVs and EVs over the same conditions, which can assist them in making the most holistic decision. One limitation is that we investigate residential charging only, with potentially meaningful differences for those who cannot or do not charge at home [21, 22].
Data availability statement
All data that support the findings of this study are included within the article (and any supplementary files).