Plug-in Hybrid Economy Calculator

How to use this plug-in hybrid economy calculator

What this calculator does

This calculator estimates how a plug-in hybrid electric vehicle (PHEV) divides monthly driving between grid electricity and gasoline, then translates that split into a real-life miles-per-gallon-equivalent result, monthly energy cost, savings against a gasoline-only comparison car, and a simple fuel-savings payback period. It is designed for planning and comparison, not for predicting a specific trip. The model assumes the battery starts each modeled trip with its full usable electric range and that the vehicle uses electricity first, then gasoline. Actual PHEVs can blend both power sources and can consume more or less energy because of weather, speed, accessories, terrain, charging losses, or battery condition. The U.S. Department of Energy explains the same basic operating pattern in its guide to plug-in hybrid electric vehicles.

When to use it

Use the calculator when comparing a PHEV with a conventional car, deciding whether your commute fits within an electric range, estimating how gasoline-heavy long trips affect operating cost, or checking whether a higher PHEV purchase price could be recovered through energy savings. It is also useful for testing a home-versus-work charging price mix before committing to a particular charging routine.

How to calculate

1. The calculator opens with a complete Toyota Prius Prime demonstration scenario, so the results, cost chart, detail table, and example XLSX are immediately usable. Replace any demonstration value with your own current assumptions.
2. Choose a Car model preset or edit the vehicle specification fields. If you edit a preset specification, the selector changes to Custom vehicle so your inputs remain explicit.
3. Enter your typical short and long trips, then enter local gasoline and electricity prices. Turn on Tiered electricity pricing only when you genuinely use two charging prices; the calculator blends those rates by the Tier 1 charging share.
4. Enter the conventional-car MPG and purchase-cost comparison. Read Your MPGe, monthly costs, PHEV savings, and the payback result. Then use Download Excel to export the current validated scenario.
5. Reset clears the demonstration and all user-entered semantic data. After Reset, Download Excel is disabled until a complete valid scenario is entered again.

Input guide

Car model is a required preset/custom selector. The demonstration uses Toyota Prius Prime (2017). A preset fills Range on battery, Car cost, Consumption rate, and MPG (gas only); editing those fields switches to Custom vehicle. Range on battery is required miles greater than zero, such as 25 mi. A higher range shifts more long-trip miles to electricity. Do not enter a nominal battery capacity here. Car cost is a required nonnegative U.S.-dollar amount, such as $27,100, used only in the payback calculation. Consumption rate is required kWh per 100 miles greater than zero, such as 25; higher consumption raises electricity cost and lowers MPGe. MPG (gas only) is required gasoline fuel economy greater than zero, such as 54 mpg; higher MPG reduces gasoline use on battery-depleted miles.

Average short-trip distance is required miles per trip and must be between zero and the battery range when short trips are present; the example uses 15 mi. Short trips per month is a required nonnegative whole number, 20 in the example. These trips are modeled entirely on battery. Average long-trip distance is required miles per trip and must exceed the battery range when long trips are present; the example uses 120 mi. Long trips per month is a required nonnegative whole number, 4 in the example. Each long trip uses up to one full battery range, with the remainder assigned to gasoline. A common mistake is entering one-way distance in one field and round-trip distance in another; use one consistent definition.

Gas price is required dollars per U.S. gallon, $3.50/gal in the example. Electricity price is required dollars per kWh, $0.16/kWh in the example. The calculator accepts standard U.S. decimal notation and rejects ambiguous decimal-comma or scientific notation. Tiered electricity pricing is optional and off by default. When enabled, Tier 2 electricity price is a required nonnegative $/kWh rate and Tier 1 charging share is a required percentage from 0% through 100%. For example, 70% at $0.16/kWh and 30% at $0.08/kWh yields a weighted $0.136/kWh rate. Do not use a zero tier merely to force a lower result unless some charging energy is truly free.

MPG of a regular car is required and greater than zero; the example uses 30 mpg. Use a city, highway, or combined rating that matches the driving you are modeling. Regular car cost is a required nonnegative purchase price, $24,000 in the example. Charging station cost is a required nonnegative incremental amount, $1,200 in the example; use $0 if no incremental equipment expense applies. Government incentive/grant is a required nonnegative amount and is $0 in the demonstration. Eligibility rules change, so include only an incentive you have independently confirmed rather than assuming one applies.

Output guide

Monthly miles is the sum of all modeled trip miles. Battery share is the percentage of those miles assigned to electricity. Distance on battery and Distance on gas are exact model allocations in miles. Your MPGe expresses combined battery and gasoline energy in miles per gallon gasoline equivalent; it is an energy-equivalent estimate, not the gasoline MPG you would observe at the pump. The U.S. EPA explains MPGe and the 33.7 kWh-per-gallon energy equivalence in its overview of fuel economy and EV range testing.

Electricity cost is battery kWh multiplied by the active electricity rate. Gas cost is PHEV gasoline gallons multiplied by Gas price. Their sum is Total energy costs. Expenses (gas) is what the regular car would spend on gasoline for the same monthly miles. PHEV savings is regular-car gas expense minus PHEV electricity and gas expense; a negative value means the PHEV energy bill is higher under the entered assumptions. Extra upfront cost equals PHEV price plus charging-station cost minus incentive minus regular-car price. Investment pays off after divides positive extra upfront cost by positive annualized PHEV savings; if savings are not positive, the page reports no fuel-savings payback instead of displaying infinity. The cost-split chart and the Monthly energy detail table show the same battery-electricity and gasoline costs used by these outputs.

Worked example

The startup example uses a 25-mile electric range, 25 kWh/100 mi electric consumption, and 54 mpg gas-only efficiency. Twenty 15-mile short trips contribute 300 battery miles. Four 120-mile long trips contribute another 100 battery miles and 380 gas miles, for 400 battery miles and 380 gas miles total. Electric driving uses 100.00 kWh and costs $16.00 at $0.16/kWh. Gas driving uses about 7.04 gallons and costs $24.63 at $3.50/gal, producing a $40.63 monthly PHEV energy bill. A 30-mpg conventional car would use 26 gallons over the same 780 miles and cost $91.00, so the modeled PHEV saves $50.37 per month. Using the EPA energy equivalence, the combined result is 77.97 MPGe. The $4,300 extra upfront amount divided by twelve months of modeled savings gives a simple payback of about 7.11 years.

Learn more

Charging frequency and electric-range utilization strongly influence PHEV fuel use. The Department of Energy's vehicle cost calculator methodology describes a related electricity-first, gasoline-after-range approach for PHEV travel. For charging context, the DOE also explains how workplace and public charging can reduce gasoline use in its public EV charging guidance.