What this is
A physics model of electric vehicle road trips, built from first principles. From a vehicle's road load, mass, usable battery and charging curve, it finds range at any speed, charging time between any two battery levels, and the maximum achievable average speed: the sweet spot between driving faster (more drag) and charging longer (slower as the battery fills). Nothing is curve fit to look right.
It assumes a steady speed, 68 °F, no wind, near sea level air and a 650 W accessory load (climate control, 12 volt system, lights). Change these under Trip conditions.
How it is checked, every vehicle shown, outliers included: against each car's window sticker on the EPA drive cycles page (most hand checked vehicles within a few percent, a few well off; the automatically matched EPA vehicles spread wider), and against independent 70 mph road tests on the vehicle summaries page.
Why the charger detour is one number
The time to get off the road to a charger and back is paid at every stop, whether you charge a little or a lot there. So no single charger's detour changes when you should unplug; only the average detour over the trip does, because it sets how many stops the trip needs. With the same arrival percentage and the same charge curve at every stop, the best unplug point is the same at every stop. This was checked by brute force on random trips with detours from 3 to 15 minutes: charging to the average detour optimum at every stop matched the best possible plan, and every stop by stop variation lost time. The model assumes a charger is available wherever you reach your arrival percentage; when the next charger you intend to use is farther than that, distance sets the floor, not the sweet spot.
The vehicles
Hand checked vehicles were added one at a time; the vehicle summaries page shows where each number comes from.
Vehicles from US EPA data cover every battery electric model for 2022 to 2027 that EPA tested. Each pairs the window sticker with the road load of a car EPA tested, and its usable battery is worked out from the sticker, so it is an estimate. EPA often tests one model in several setups (wheels, tires, options), each with its own road load. A setup that does not fit the energy the sticker reports is left out. When the name decides, that setup is used; when it does not, every possible setup is listed, least drag first, so you can keep the one that behaves most like your car. A few use a different model's test car (an Equinox EV tested as a Blazer EV) and could be well off. The ⓘ line under the vehicle button says how each one was matched.
Charging curves
Each curve's source is named in the charging chart title. Curves credited to @OutofSpecReviews are Out of Spec Studios' published charging tests; the BrightDrop 600 curve (@lightpowered) is Power of Light's own data.
How exact is a curve? Each is one charging session on one car. Temperature, battery health and the charger all change the charge rate, so read charging times as a good estimate, not a promise.
Not measured on your exact car? The chart subtitle says when a curve comes from another year or trim, was traced from a video, or was built from a maker's claims. Vehicles from US EPA data have no curve of their own, but you can borrow one from a similar car in the ⚡ Charging curve list under the vehicle button. Its power is used as measured, not scaled for battery size.
Data sources (US government, public domain)
- EPA test car list (road load coefficients, test weights): epa.gov
- EPA certified vehicle test results, model years 2014 to present (road load and test weights for the vehicles from US EPA data): epa.gov
- DOE and EPA Fuel Economy Guide (sticker ranges, MPGe, adjustment factors): fueleconomy.gov
- EPA dynamometer drive schedules (UDDS city, HWFET highway): epa.gov
The 0.7 default label adjustment factor follows 40 CFR § 600.210-12(d)(3); each vehicle's own factor is used where the EPA data provides it.
Privacy
This site sets no cookies, runs no analytics, shows no ads, and loads nothing from third parties. The web server keeps standard access logs (IP address, page, time, browser and referring page) for about a month, and nothing else. Your preferences, last setup and any borrowed curve stay in your own browser and never leave your device; the physics runs entirely in your browser. YouTube and Venmo links are plain links, not embedded players.
License
Copyright © 2026 Feather Solar, LLC.
Licensed under the GNU General Public
License v3.0. This program is free software: you can redistribute it and/or modify it
under the terms of the GPL as published by the Free Software Foundation, either version 3
of the License, or (at your option) any later version. It is distributed in the hope that
it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.