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PHEV economy calculator

A 100-mile trip with 40 miles of electric range, 28 kWh per 100 miles and 50 mpg on gas uses 11.2 kWh and 1.2 gallons, folded into one MPGe figure. Enter your own numbers to rate the drive you actually make. Free in your browser.

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Worked example

If you enter

Electric range: 40
Electric efficiency: 28
Gas economy: 50
Trip distance: 100

You get

Electric miles: 40
Gas miles: 60
Electricity kwh: 11.2
Gasoline gallons: 1.2

A plug-in hybrid electric vehicle (PHEV) spends the first miles of a trip on stored charge and the rest on gasoline, so neither the electric MPGe nor the charge-sustaining MPG by itself describes a commute you actually drive. This PHEV economy calculator accepts four finite numbers — electric range in miles, charge-depleting electric efficiency in kilowatt-hours per one hundred miles, charge-sustaining gas economy in miles per gallon, and trip distance in miles — and returns miles per gallon equivalent (MPGe) for that trip. Electricity is converted with the EPA gasoline-gallon equivalent of 33.705 kilowatt-hours per gallon of gasoline. Miles beyond the electric range burn fuel at the gas economy you send.

How a plug-in hybrid trip becomes MPGe

A plug-in hybrid has two operating modes on every trip. In charge-depleting mode the traction battery supplies the miles until it is empty, or until the trip ends, whichever comes first. In charge-sustaining mode the gasoline engine and hybrid system hold the battery near a target state of charge and the vehicle behaves like an ordinary hybrid.

For a trip of D miles and an electric range of R miles, the electric miles are the minimum of R and D, and the gasoline miles are the remainder max(0, D minus R). Electric energy in kilowatt-hours is those electric miles times the charge-depleting efficiency in kilowatt-hours per one hundred miles, divided by one hundred. Gasoline volume in gallons is the gasoline miles divided by the charge-sustaining miles per gallon.

Miles per gallon equivalent then follows the EPA energy-equivalence definition: divide the trip distance by the sum of gasoline gallons and the gasoline-gallon equivalent of the electricity, where one gallon of gasoline equals 33.705 kilowatt-hours. When the trip is shorter than the electric range, gasoline gallons are zero and MPGe is simply 3370.5 divided by the kilowatt-hours per one hundred miles — the same conversion the window sticker uses for an all-electric figure. When the electric range is zero the result collapses to the gas economy you sent.

This is a trip MPGe, not the EPA utility-factor-weighted combined rating on a Monroney label: that rating assumes a statistical mix of trips, while this calculator answers the commute you actually typed.

What to enter and in which units

A gas economy of zero is rejected because gasoline gallons are undefined when gas economy is zero — those failures are not billed. Negative range, efficiency, gas economy or distance is rejected the same way. Numbers are rounded to twelve decimal places so goldens and clients compare byte-for-byte across runtimes.

There is no network lookup, no random draw, and no dependence on the current date.

Who gets the most from a plug-in hybrid trip figure

Drivers comparing a plug-in hybrid against a gasoline car need a trip MPGe, not a unit converter that only restates MPG as litres per one hundred kilometres, and not an all-electric charging-cost tool that never burns a gallon. Fleet managers who already log electric range, sticker kWh per one hundred miles, charge-sustaining MPG and daily mileage can post one task per vehicle and store mpge beside the route identifier without opening a spreadsheet of 33.705 factors. Failed validation does not consume balance.

Keep requests small, pin the rounded fields in tests, and you get a reproducible plug-in hybrid MPGe without standing up a vehicle telemetry stack of your own.

What you can do with it

Commute MPGe for a plug-in hybrid

Turn your electric range, sticker kWh/100 mi, charge-sustaining MPG and daily miles into the MPGe that commute actually delivers.

Fleet and lease comparisons

Score each PHEV route against a gasoline car with a deterministic trip MPGe instead of quoting the window-sticker combined rating.

Showroom and classroom checks

Let a visitor or student submit range, efficiency, gas MPG and distance and see all-electric, blended or all-gasoline MPGe without a spreadsheet.

FAQ

How is PHEV miles per gallon equivalent calculated?

Electric miles are min(electric range, trip distance). Gasoline miles are the remainder. Kilowatt-hours equal electric miles times kWh/100 mi divided by 100. Gallons equal gasoline miles divided by gas MPG. MPGe is trip distance divided by (gallons + kWh / 33.705).

What happens if gas economy is zero?

Gasoline gallons are undefined when gas economy is zero, so the calculator refuses that input instead of dividing by zero. Invalid input is not billed.

Is this the same as the EPA window-sticker PHEV rating?

No. The sticker combines charge-depleting and charge-sustaining results with a statistical utility factor. This calculator uses your trip distance, so a short commute can be all-electric while a long highway run is blended.

What units does the PHEV economy calculator expect?

Convert mi/kWh with 100 / (mi/kWh) before sending.

What if my trip is shorter than the electric range?

Then the whole trip runs on the battery, no gasoline is counted, and the result is simply 3370.5 divided by your kWh per 100 miles, the same all-electric conversion the window sticker uses.

Related tools

For developers — API access

Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.

API endpoint

POSThttps://api.kit.forhosting.com/eco/phev-economy

Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.

Call it from your stack

curl -X POST https://api.kit.forhosting.com/eco/phev-economy \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"electric_range":40,"electric_efficiency":28,"gas_economy":50,"trip_distance":100}'

const res = await fetch("https://api.kit.forhosting.com/eco/phev-economy", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "electric_range": 40,
    "electric_efficiency": 28,
    "gas_economy": 50,
    "trip_distance": 100
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/eco/phev-economy",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "electric_range": 40,
    "electric_efficiency": 28,
    "gas_economy": 50,
    "trip_distance": 100
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/eco/phev-economy", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"electric_range":40,"electric_efficiency":28,"gas_economy":50,"trip_distance":100}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"electric_range":40,"electric_efficiency":28,"gas_economy":50,"trip_distance":100}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/eco/phev-economy", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "electric_range": 40,
  "electric_efficiency": 28,
  "gas_economy": 50,
  "trip_distance": 100
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "eco.phev_economy",
  "status": "queued",
  "_links": {
    "result": "/tasks/tsk_…/result"
  }
}

The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.

Pricing

Per request$0.002

Published price — no tokens, no invented credits. A failed task is never charged.

Errors

HTTP	Code	Meaning
`401`	`unauthorized`	Missing or invalid API key.
`402`	`insufficient_balance`	Your balance doesn't cover the task price.
`404`	`unknown_type`	That task type doesn't exist.
`429`	`rate_limited`	Too many requests. Use the webhook instead of polling.

Technical notes

A gas economy of zero is rejected as invalid_input because gasoline gallons would be undefined.

Input contract, units, aliases and error behaviour

Send a JSON object with four required finite numbers. electric_range is the charge-depleting electric range in miles; zero is allowed and means the battery is empty or the vehicle has no plug-in range. electric_efficiency is charge-depleting consumption in kilowatt-hours per one hundred miles, the EPA sticker convention; convert miles per kilowatt-hour with one hundred divided by that figure. gas_economy is charge-sustaining gasoline fuel economy in United States miles per gallon once the battery is depleted, and it must be strictly greater than zero. trip_distance is the length of the trip in miles and must be positive. Each field also accepts a numeric string and a short list of aliases (ev_range, range, cd_range, electric_range_mi, ev_efficiency, consumption, kwh_per_100, electric_consumption, mpg, gas_mpg, cs_mpg, gasoline_mpg, distance, trip, miles, trip_miles) so spreadsheets and forms do not have to rename columns. Missing fields, empty strings, booleans, objects and tokens that are not plain decimal or scientific numbers fail with invalid_input that names the field. On success the body echoes the four inputs, reports electric_miles and gas_miles, electricity_kwh, gasoline_gallons, electric_gge, total_gge, mpge, the trip utility_factor (electric miles over trip distance), the constant kwh_per_gallon 33.705, a charge_mode of all_electric, blended or all_gasoline, a compact formula string, and the method label cd_cs_trip_mpge.

Where a PHEV economy API earns its keep

Dealers who want to show a commuter that a twenty-mile round trip stays all-electric can send the same four numbers the visitor already typed and display charge_mode all_electric without inventing a utility factor. If you later need dollars, multiply gasoline_gallons and electricity_kwh by local prices; this endpoint stops at energy-equivalent economy on purpose, so the MPGe stays an honest function of the four numbers you sent.

Technical questions

What does the PHEV economy calculator cost?

The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.

Read the full KIT documentation →

Run — free