Fuel Cost Calculator

A fuel cost calculator is a mathematical framework used to determine the exact financial expense, efficiency, and environmental impact of operating a motor vehicle over a specific distance. By synthesizing variables such as distance traveled, vehicle fuel efficiency, and current energy prices, this concept allows drivers, logistics professionals, and economists to accurately forecast transportation budgets. Readers of this comprehensive guide will learn the foundational formulas behind fuel consumption, the historical evolution of efficiency standards, advanced strategies for minimizing travel expenses, and how to accurately calculate the carbon emissions of any road trip.

What It Is and Why It Matters

At its core, a fuel cost calculator is an applied mathematical model that translates physical distance and mechanical efficiency into a tangible financial figure. When a person drives a vehicle from point A to point B, the engine combusts a specific volume of fuel to generate the kinetic energy required to move the mass of the vehicle against the forces of friction and aerodynamic drag. Because fuel is a commodity sold by volume (gallons or liters), and vehicles consume this volume at varying rates depending on their engineering, it is impossible to know the cost of a trip simply by looking at a map. The fuel cost calculation bridges this gap, providing a precise dollar amount for any given journey.

Understanding and applying this calculation matters immensely for several distinct groups of people. For the everyday commuter, it provides the necessary data to build an accurate household budget, revealing exactly how much of their monthly income is burned on the highway. For families planning a cross-country road trip, it transforms an unpredictable variable into a fixed line-item, allowing them to decide whether driving is actually more economical than purchasing airline tickets. For independent contractors, delivery drivers, and rideshare operators, mastering fuel cost calculation is the difference between operating at a profit and operating at a loss.

Beyond personal finance, this concept is critical on a macroeconomic and environmental scale. Fuel consumption directly correlates with greenhouse gas emissions. Every gallon of gasoline burned releases a specific mass of carbon dioxide into the atmosphere. Therefore, the exact same mathematical formulas used to calculate the cost of a trip are used by environmental scientists and policymakers to calculate the carbon footprint of our transportation infrastructure. By mastering these calculations, individuals gain the power to make informed, data-driven decisions about where they live, what they drive, and how they travel.

History and Origin of Fuel Economy and Cost Tracking

The necessity of calculating fuel costs is as old as the automobile itself, but the standardization of how we measure and discuss fuel efficiency has a distinct and turbulent history. In the early days of motoring, at the dawn of the 20th century, fuel efficiency was rarely standardized. When Henry Ford introduced the Model T in 1908, it achieved roughly 13 to 21 miles per gallon, but fuel was purchased at hardware stores or pharmacies, and the concept of a "road trip budget" was virtually nonexistent. Motoring was a luxury, and those who could afford the vehicle could generally afford the fuel.

The turning point in the history of fuel calculation occurred during the 1973 OPEC oil embargo. In October 1973, the Organization of Arab Petroleum Exporting Countries proclaimed an oil embargo targeted at nations perceived as supporting Israel during the Yom Kippur War. The price of oil quadrupled globally, jumping from roughly $3.00 per barrel to nearly $12.00 per barrel. Suddenly, American drivers were waiting in miles-long lines at gas stations, and the cost of commuting became a national crisis. This geopolitical shock forced the United States government to intervene in automotive engineering and consumer awareness.

In response, the U.S. Congress passed the Energy Policy and Conservation Act of 1975, which established the Corporate Average Fuel Economy (CAFE) standards. This legislation mandated that automakers dramatically improve the fuel efficiency of their fleets. To ensure consumers could make informed decisions, the Environmental Protection Agency (EPA) was tasked with testing vehicles and, in 1977, mandated the now-famous "window sticker" on all new cars, prominently displaying the estimated Miles Per Gallon (MPG). This standardized metric gave the general public the baseline variable they needed to accurately calculate their fuel costs. By the late 1980s and 1990s, automotive engineers began integrating digital trip computers into vehicle dashboards, using electronic fuel injection data to calculate and display real-time fuel consumption, automating the math that drivers had previously done with a pencil and a gas station receipt.

Key Concepts and Terminology

To accurately calculate and discuss fuel costs, one must master the specific terminology used in the automotive and energy sectors. Without a firm grasp of these variables, any mathematical calculation will be fundamentally flawed.

Miles Per Gallon (MPG): The standard unit of measurement for fuel efficiency in the United States, the United Kingdom, and a few other nations. It represents the distance in miles a vehicle can travel on a single liquid gallon of fuel. A higher MPG indicates a more efficient vehicle. MPG is typically divided into "City MPG" (stop-and-go traffic, which consumes more fuel) and "Highway MPG" (steady speeds, which consumes less fuel).

Liters per 100 Kilometers (L/100km): The standard metric for fuel efficiency used in most of the world, including Europe, Canada, and Australia. Unlike MPG, which measures distance per unit of volume, L/100km measures volume per unit of distance. Therefore, a lower number indicates a more efficient vehicle.

Odometer and Trip Meter: The odometer is the instrument on the dashboard that records the total lifetime distance the vehicle has traveled. The trip meter is a resettable sub-function of the odometer used to measure the distance of a specific journey or the distance driven on a single tank of gas.

Fuel Capacity and Range: Fuel capacity is the total volume of fuel the vehicle's gas tank can hold (e.g., 14 gallons). Range is the maximum distance the vehicle can travel on a full tank, calculated by multiplying the fuel capacity by the vehicle's average MPG.

Price per Unit: The retail cost of fuel at the pump, usually expressed in dollars per gallon ($/gal) or dollars per liter ($/L). This price fluctuates daily based on crude oil prices, refining costs, distribution logistics, and local taxes.

Emission Factor: A standardized multiplier used to calculate the environmental impact of burning fuel. For standard E10 unleaded gasoline (gasoline containing 10% ethanol), the combustion of one gallon produces approximately 17.6 pounds of carbon dioxide (CO2). For diesel fuel, the emission factor is roughly 22.4 pounds of CO2 per gallon.

How It Works — Step by Step

Calculating fuel costs requires a straightforward algebraic process. You must determine how much fuel a journey will require, and then multiply that volume by the cost of the fuel. Here is the complete, step-by-step mathematical breakdown.

The Core Formulas

To find the total cost of a trip, you need three pieces of information: Distance ($D$), Fuel Efficiency ($E$), and Price per unit of fuel ($P$).

Step 1: Calculate the Fuel Required If you are using US standard measurements (Miles and MPG), the formula to find the Total Gallons Needed ($G$) is: $G = D / E$ (Total Gallons = Total Miles / Miles Per Gallon)

Step 2: Calculate the Total Cost Once you know the gallons required, multiply it by the Price per Gallon ($P$) to find the Total Cost ($C$): $C = G \times P$ (Total Cost = Total Gallons \times Price per Gallon)

Combined Formula: $C = (D / E) \times P$

Full Worked Example (US Standard)

Imagine a 32-year-old sales representative is planning a road trip from Chicago, Illinois, to Nashville, Tennessee. The distance is exactly 470 miles one-way. She drives a 2019 Honda Accord that averages 32 MPG on the highway. The current average price of gasoline along her route is $3.45 per gallon.

1. First, find the fuel required: 470 miles / 32 MPG = 14.6875 gallons.
2. Next, calculate the cost: 14.6875 gallons \times $3.45 = $50.67.
3. Therefore, the one-way fuel cost for this trip is $50.67. If she is driving round-trip, she simply doubles this figure for a total fuel budget of $101.34.

Full Worked Example (Metric System)

The math changes slightly when using the metric system, because efficiency is measured in Liters per 100 kilometers (L/100km). The formula for Total Liters Needed ($L$) is: $L = (D / 100) \times E$ (Total Liters = (Total Kilometers / 100) \times Liters per 100km)

Imagine a family driving from Toronto to Montreal, a distance of 540 kilometers. Their SUV consumes 8.5 Liters per 100km. The price of fuel is $1.60 CAD per liter.

1. First, find the fuel required: (540 km / 100) = 5.4.
2. Multiply by efficiency: 5.4 \times 8.5 L/100km = 45.9 liters of fuel required.
3. Calculate the cost: 45.9 liters \times $1.60 = $73.44 CAD.

Types, Variations, and Methods of Fuel Calculation

While the foundational math remains identical, the method in which people apply these formulas varies depending on their specific goal. Professionals and everyday drivers utilize different approaches to fuel calculation based on what they are trying to achieve.

Predictive vs. Retrospective Calculation

Predictive calculation is used when planning a future trip. It relies on estimates: the estimated distance from a mapping application, the EPA's estimated MPG for the vehicle, and the estimated average cost of fuel along the route. This is primarily a budgeting tool. Retrospective calculation is used after a trip is completed to determine the exact, literal cost. This requires the driver to fill their tank completely before the trip, reset their trip meter to zero, drive to their destination, and fill the tank completely again. By dividing the exact miles driven by the exact gallons purchased on the second receipt, the driver calculates their true real-world MPG, resulting in an exact financial accounting.

Commuter Annualization

This variation is used by individuals trying to understand the macroeconomic impact of their daily commute. Instead of calculating a single trip, they calculate the annual cost. For example, a person commuting 25 miles each way (50 miles daily) for 240 workdays a year drives 12,000 miles solely for work. If their car gets 24 MPG and gas averages $3.50, their annual fuel cost is (12,000 / 24) \times 3.50 = $1,750 per year. This calculation is frequently used when deciding whether to accept a new job offer that requires a longer commute.

Split-Cost Calculation

Commonly used by college students or groups of friends taking shared road trips. The total predictive or retrospective cost of the journey is calculated and then divided equally among the occupants of the vehicle. If a 1,200-mile road trip costs $180 in total fuel, and there are four people in the car, the split-cost is $45 per person. This is often compared against the cost of four individual bus or airline tickets to prove the economic viability of carpooling.

Real-World Examples and Applications

To fully grasp the utility of fuel cost calculations, one must examine how these formulas are applied in specific, concrete scenarios. The numbers involved can drastically alter financial decision-making.

Scenario 1: The Rideshare Driver's Profit Margin A 40-year-old rideshare driver works in Los Angeles, California. On an average Saturday night, he drives 150 miles over an 8-hour shift, generating $210 in gross fare revenue. He drives a V6 SUV that gets 18 MPG in city traffic, and gas costs $4.80 per gallon. His fuel calculation: 150 miles / 18 MPG = 8.33 gallons. 8.33 gallons \times $4.80 = $39.98 in fuel costs. By subtracting his fuel cost from his gross revenue ($210 - $39.98 = $170.02), he realizes his actual take-home pay is significantly lower than his gross earnings. This calculation often prompts professional drivers to trade in inefficient SUVs for hybrid vehicles.

Scenario 2: The Cross-Country Move A couple is moving from Seattle, Washington, to Austin, Texas—a distance of roughly 2,100 miles. They are debating whether to pack their belongings into their Toyota RAV4 (averaging 28 MPG) or rent a large U-Haul box truck (averaging 10 MPG). Gas averages $3.60 per gallon. RAV4 Cost: (2,100 / 28) \times 3.60 = $270.00. U-Haul Cost: (2,100 / 10) \times 3.60 = $756.00. The fuel calculation reveals a $486 difference in fuel costs alone. This massive discrepancy must be factored into the overall cost of the rental truck when deciding how to execute the move.

Scenario 3: The Hybrid Premium Payoff A buyer is looking at two versions of the same car: a standard gas version that costs $25,000 and gets 30 MPG, and a hybrid version that costs $28,000 and gets 50 MPG. The buyer drives 15,000 miles a year, and gas is $3.50 per gallon. Gas Car Annual Fuel: (15,000 / 30) \times 3.50 = $1,750/year. Hybrid Annual Fuel: (15,000 / 50) \times 3.50 = $1,050/year. The hybrid saves $700 per year in fuel. Because the hybrid costs $3,000 more upfront, the buyer divides the price premium by the annual savings ($3,000 / $700) to determine it will take exactly 4.28 years of driving to "break even" on the hybrid upgrade.

The Environmental Impact: Calculating Fuel Emissions

Fuel cost calculators are not exclusively financial tools; they are also environmental instruments. Because the chemistry of combustion is exact, the amount of fuel burned directly correlates to the mass of greenhouse gases emitted into the atmosphere. Gasoline is composed primarily of hydrocarbons. When burned, the carbon in the fuel bonds with oxygen in the air to create carbon dioxide (CO2). Because oxygen has mass, the resulting CO2 actually weighs significantly more than the fuel itself.

According to the U.S. Environmental Protection Agency, the combustion of one single liquid gallon of standard E10 unleaded gasoline produces exactly 8.887 kilograms, or 17.6 pounds, of CO2. The combustion of one gallon of diesel fuel, which is denser, produces 10.180 kilograms, or 22.4 pounds, of CO2.

The Emissions Formula: $Total CO2 = Gallons Burned \times Emission Factor$

Worked Example: Let us return to the sales representative driving 470 miles from Chicago to Nashville in a car getting 32 MPG. We previously calculated she would burn 14.68 gallons of gasoline. To find her carbon footprint for this one-way trip: 14.68 gallons \times 17.6 lbs of CO2 = 258.36 pounds of carbon dioxide emitted into the atmosphere. If a logistics company is operating a fleet of 100 delivery trucks, each burning 5,000 gallons of diesel per year, their calculation looks like this: 100 trucks \times 5,000 gallons \times 22.4 lbs = 11,200,000 pounds (or 5,600 tons) of CO2 annually. Understanding this math is the first mandatory step in corporate carbon offsetting programs.

Common Mistakes and Misconceptions

When novices attempt to calculate fuel costs, they frequently fall victim to a handful of pervasive misconceptions that render their budgets highly inaccurate. Correcting these mental models is essential for accurate forecasting.

The "MPG Illusion" The most common mathematical misconception in automotive efficiency is the linear interpretation of MPG. Most people assume that an increase of 10 MPG yields the same fuel savings regardless of the baseline. This is mathematically false. Going from a 10 MPG vehicle to a 20 MPG vehicle saves vastly more fuel than going from a 40 MPG vehicle to a 50 MPG vehicle. Proof: Over a 1,000-mile trip, a 10 MPG truck burns 100 gallons. A 20 MPG truck burns 50 gallons. Upgrading saves 50 gallons. Conversely, over a 1,000-mile trip, a 40 MPG car burns 25 gallons. A 50 MPG car burns 20 gallons. Upgrading saves only 5 gallons. The relationship between MPG and fuel consumption is an inverse curve, not a straight line.

Relying Exclusively on EPA Estimates Beginners often pull the EPA combined MPG rating from a Google search and use it as gospel for their calculations. The EPA numbers are derived from highly controlled laboratory testing on dynamometers, in perfect weather, with no cargo, and optimal tire pressure. Real-world driving involves aggressive acceleration, heavy payloads, wind resistance, and tire wear. A vehicle rated for 30 MPG highway might only achieve 24 MPG when loaded with four passengers and luggage on a windy day. Failing to discount the EPA rating by 10% to 15% for real-world variables leads to underfunded travel budgets.

Confusing Fuel Cost with Total Operating Cost Many people compare the fuel cost of driving to the cost of an airline ticket and conclude that driving is immensely cheaper. This ignores the "invisible" costs of motoring: depreciation, maintenance, and tire wear. Every mile driven brings the car closer to an oil change, wears down the brake pads, and decreases the resale value of the vehicle. While the gas for a 1,000-mile trip might only cost $120, the actual cost of operating the vehicle is much higher, which is why business reimbursement rates are significantly higher than the raw cost of fuel.

Best Practices and Expert Strategies for Fuel Efficiency

Professionals whose livelihoods depend on minimizing transportation costs do not accept their vehicle's base MPG as a fixed rule. They employ a variety of behavioral and mechanical strategies to manipulate the variables in the fuel cost equation, actively reducing the amount of fuel burned per mile.

Hyper-Miling Techniques "Hyper-miling" is the practice of altering driving habits to maximize fuel efficiency. The most impactful technique is managing the accelerator and brake pedals. Every time a driver uses the brakes, they are taking kinetic energy (which they paid for with fuel) and turning it into useless heat via brake pad friction. Experts anticipate traffic flow, coasting to red lights rather than accelerating toward them and braking hard. Furthermore, aerodynamic drag increases exponentially with speed. Driving 75 mph instead of 65 mph can reduce fuel economy by up to 15% because the engine has to work exponentially harder to push through the air.

Aerodynamic and Weight Management The physical state of the vehicle drastically alters the math. Roof racks, cargo boxes, and even driving with the windows rolled down at highway speeds destroy the aerodynamic profile of the car. According to the Department of Energy, a large roof cargo box can reduce fuel economy by 10% to 25% at interstate speeds. Experts remove roof racks when not in use. Additionally, weight is a critical factor. For every 100 pounds of excess weight in the vehicle, fuel economy drops by roughly 1%.

Tire Pressure Optimization The rolling resistance of a vehicle's tires is a massive factor in fuel consumption. When tires are under-inflated, more of the rubber touches the road, increasing friction and requiring the engine to burn more fuel to maintain speed. The standard rule of thumb is that gas mileage decreases by 0.2% for every 1 pound per square inch (psi) drop in the average pressure of all four tires. Experts check their tire pressure monthly with a digital gauge, ensuring it matches the manufacturer's recommendation printed on the inside of the driver's door jamb.

Edge Cases, Limitations, and Pitfalls

Even the most meticulous fuel cost calculations will break down when subjected to extreme edge cases. The mathematical formulas assume a relatively standard driving environment, and when reality diverges from that standard, the numbers fail.

Towing and Heavy Payloads When a truck or SUV is used to tow a boat, a camper, or a heavy trailer, its baseline MPG becomes completely irrelevant. Towing introduces massive aerodynamic drag and thousands of pounds of extra mass. A pickup truck that normally achieves 22 MPG on the highway might plummet to 9 or 10 MPG when towing a 5,000-pound travel trailer. There is no reliable mathematical formula to predict towing MPG without specific drag coefficients; it must be measured retrospectively.

Extreme Weather Conditions Temperature plays a massive role in internal combustion efficiency. In extreme cold (below 20°F / -6°C), engine oil thickens, increasing internal friction. Furthermore, cold air is denser, increasing aerodynamic drag. The EPA notes that a conventional car's fuel economy is about 15% lower at 20°F than it is at 77°F for a typical city commute. Conversely, in extreme heat, running the vehicle's air conditioning compressor heavily burdens the engine, reducing fuel economy by roughly 5% to 25% depending on the vehicle size and speed.

Idling and Traffic Congestion The fundamental formula ($G = D / E$) requires distance to function. When a vehicle is idling in gridlock traffic, at a drive-through, or warming up in a driveway, it is burning fuel but traveling zero miles. At idle, a vehicle achieves 0 MPG. A standard engine consumes roughly 0.2 to 0.5 gallons of fuel per hour of idling. If a calculation is made for a 20-mile commute, but that commute involves 45 minutes of dead-stopped traffic, the actual fuel consumed will be vastly higher than the formula predicts.

Industry Standards and Benchmarks

To understand whether a specific fuel cost is "good" or "bad," one must compare it against established industry benchmarks. These standards are set by government agencies and massive logistical organizations.

The EPA Testing Cycles In the United States, the benchmark for vehicle efficiency is established by the EPA using specific dynamometer tests. The "City" benchmark is based on the FTP-75 (Federal Test Procedure), which simulates an 11-mile urban route with frequent stops, an average speed of 21.2 mph, and a top speed of 56 mph. The "Highway" benchmark is based on the HWFET (Highway Fuel Economy Test), simulating a 10-mile trip without stops, averaging 48.3 mph. When discussing standard MPG, professionals are referring to the results of these specific, highly regulated tests.

Fleet Averages To know if a vehicle is efficient compared to the modern standard, one looks at the national fleet average. According to the EPA's Automotive Trends Report, the estimated real-world fuel economy for all new light-duty vehicles sold in the United States in recent model years hovers around 25.4 to 26.0 MPG. Therefore, a vehicle achieving 35 MPG is objectively highly efficient by modern standards, while a vehicle achieving 15 MPG is highly inefficient.

The IRS Standard Mileage Rate For business, medical, or charitable purposes, the United States Internal Revenue Service (IRS) establishes a standard benchmark for the total cost of operating a vehicle. For the tax year 2024, the IRS standard mileage rate is 67 cents per mile driven for business use. This is a critical benchmark because it represents the comprehensive cost of driving. If a person calculates their raw fuel cost at 12 cents per mile, the IRS benchmark reminds them that the remaining 55 cents per mile accounts for depreciation, insurance, repairs, and tires.

Comparisons with Alternatives (EVs, Public Transit, Flights)

The fuel cost calculator is most powerful when used as a comparative tool to evaluate alternative modes of transportation. By quantifying the cost of driving, one can make rational, economically sound decisions regarding how to travel.

Internal Combustion vs. Electric Vehicles (EVs) Comparing a gas car to an EV requires translating gallons into electricity. EVs are measured in kilowatt-hours per 100 miles (kWh/100mi) or MPGe (Miles Per Gallon equivalent). To calculate the "fuel" cost of an EV, you multiply the kWh required to drive a specific distance by the local cost of electricity per kWh. For example, an EV might consume 30 kWh to drive 100 miles. If residential electricity costs $0.15 per kWh, driving 100 miles costs $4.50 (30 \times 0.15). A 30 MPG gas car driving 100 miles requires 3.33 gallons. At $3.50 a gallon, the gas car costs $11.65. The calculation proves the EV operates at less than half the energy cost of the gas vehicle.

Driving vs. Flying When calculating the cost of a long-distance trip, the fuel calculation must be weighed against airline tickets. A 1,000-mile trip in a 25 MPG car with $3.50 gas costs $140 in fuel. However, if four family members are traveling, that $140 total is compared against four $300 airline tickets ($1,200 total). In this scenario, driving is overwhelmingly cheaper. If a solo traveler is making the same trip, comparing the $140 gas cost (plus vehicle wear and tear, and hotel stays) against a single $300 flight might make flying the more economically rational choice.

Driving vs. Public Transit For daily commuting, fuel calculations are compared against fixed transit passes. If a commuter calculates their monthly fuel cost to be $120, and parking downtown costs $150 a month, their total driving expense is $270. If a monthly unlimited metropolitan train pass costs $100, the mathematical comparison clearly dictates that public transit is the superior financial choice, saving the commuter $1,700 annually.

Frequently Asked Questions

How do I calculate fuel cost if my driving is a mix of city and highway? To calculate a mixed driving route, you must use a weighted average based on the percentage of miles driven in each environment. If you drive 100 miles total, with 70 miles on the highway (at 30 MPG) and 30 miles in the city (at 20 MPG), you calculate them separately. The highway portion burns 2.33 gallons (70/30) and the city portion burns 1.5 gallons (30/20). Add them together for a total of 3.83 gallons, then multiply by the price of fuel. Most modern vehicles display a "Combined MPG" on the dashboard that does this math for you dynamically.

Does using premium gas improve fuel economy enough to justify the cost? In the vast majority of cases, no. Premium gas simply has a higher octane rating, which makes it more resistant to pre-ignition (engine knock) in high-compression engines. If your vehicle's manual specifies that premium fuel is "required," you must use it to prevent engine damage and maintain optimal MPG. However, if the manual says premium is merely "recommended" or specifies regular unleaded, putting premium gas in the tank will not meaningfully increase your MPG. The tiny potential gain in efficiency is completely erased by the 20% to 30% price markup of premium fuel.

How does the air conditioning affect my fuel consumption? Air conditioning is the single largest auxiliary drain on a vehicle's engine. The A/C compressor is powered by a belt connected directly to the engine's crankshaft. Engaging it requires the engine to work harder, burning more fuel. According to the EPA, running the A/C in hot weather can reduce a vehicle's fuel economy by up to 25%, particularly on short trips. However, at highway speeds (over 60 mph), rolling the windows down creates immense aerodynamic drag that actually wastes more fuel than running the air conditioning.

What is the "MPG illusion" and why does it matter? The MPG illusion is the false belief that fuel efficiency scales linearly. It matters because it causes consumers to make poor financial decisions when buying cars. People often think upgrading from a 30 MPG car to a 40 MPG car (a 10 MPG jump) saves the same amount of gas as upgrading from a 10 MPG truck to a 20 MPG truck (also a 10 MPG jump). In reality, over 10,000 miles, the truck upgrade saves 500 gallons of gas, while the car upgrade saves only 83 gallons. The lower your current MPG, the more money you save by upgrading.

How accurately do dashboard trip computers measure fuel economy? Dashboard computers are generally accurate within 5% to 10%, but they are almost always optimistic. They calculate fuel consumption by measuring the pulse width of the fuel injectors—essentially counting how many microscopic squirts of fuel are sent into the engine. However, they cannot account for variations in fuel density, tire wear, or slight calibration errors over time. For the most accurate calculation, drivers should manually track their miles driven divided by the gallons purchased at the pump over three or four consecutive fill-ups.

How do I calculate fuel costs for a plug-in hybrid electric vehicle (PHEV)? Calculating fuel costs for a PHEV requires two separate equations. First, you determine the cost of the electric range. If the battery provides 30 miles of range and takes 10 kWh to charge at $0.15/kWh, the first 30 miles cost $1.50. Once the battery is depleted, the vehicle operates like a standard gas car. If your total trip is 100 miles, you subtract the 30 electric miles. The remaining 70 miles are calculated using the vehicle's gas MPG and the local price per gallon. You then add the electric cost ($1.50) to the gas cost to find the total trip expense.