How Charge & Explore ranks a charging stop
Most charging maps answer one question: where is the nearest plug? Charge & Explore asks a second one: of the stops you can reach, which gives you the best break while the car charges? This page explains exactly how that ranking is built, what data it uses, and where its limits are.
1. Finding the chargers
Charger locations come from the Alternative Fuel Stations dataset that the U.S. Department of Energy publishes through the National Renewable Energy Laboratory's developer API. It covers public stations in the United States and Canada and includes each station's connector types, network, and the number of charging ports. We keep each station's source record ID with the data so a listing can always be traced back to where it came from.
This dataset describes where chargers are and what they offer. It does not tell us, minute by minute, whether a stall is free or working. When a live availability feed is not available, the app does not pretend to know.
2. Keeping every suggestion reachable
Before anything is ranked, the app removes chargers you may not be able to reach. It estimates a conservative driving range from your battery size and current state of charge and then keeps a 30 percent safety margin on top. A charger outside that margin is never offered as "the best stop", and if nothing is close enough the app tells you to charge before heading further.
3. Estimating how long you will charge
Fast charging is not linear. A battery accepts its highest power when it is fairly empty and tapers as it fills, so the last 15 to 20 percent can take as long as a much larger chunk at the start. A simple "energy divided by charger power" estimate therefore underestimates any session that charges high.
Charge & Explore models the session band by band. The battery is split into state-of-charge ranges (in the default curve: 0–20%, 20–40%, 40–55%, 55–70%, 70–85% and 85–100%), and each band gets a share of the peak power that falls as the pack fills. Peak power is the lower of what your vehicle profile can accept and what the station can deliver. The estimate also allows for conversion losses and a couple of minutes to plug in and start. For stops near you it estimates the time to reach 80 percent.
The result is always shown as a range, roughly 15 percent either side of the middle estimate, rather than one exact number.
4. Ranking the chargers near you
For the "chargers near you" list and the single best stop shown when you open the app, reachable chargers are ranked with a simple, transparent score: 55 percent comes from charging power (compared against 250 kW) and 45 percent from closeness, which falls off smoothly with distance. The top eight are shown with their network, address, number of fast-charging ports from the station data, the estimated charge time and directions. Places to eat, walk or browse within about 800 metres are looked up for a stop when you open it. Place data comes from OpenStreetMap and, where enabled, Google Places.
5. The full Stop Score
The ranked demo uses the fuller model the app is built around: a 0–100 Stop Score that weighs seven named parts. The weights are published here so the ranking can be checked.
| Component | Weight | What it measures |
|---|---|---|
| Route convenience | 25% | How far the stop takes you off your route. The score falls smoothly with detour time: no detour scores 100, a 12-minute detour scores about 37. |
| Charger quality | 20% | Charging power (half of this part), number of stalls (a quarter), reliability, and live availability only when it comes from an authorized, fresh feed. |
| Amenities | 20% | The quality of food, shops and places to spend the wait. |
| Time fit | 15% | Whether the charge window is long enough to do something. The score peaks for a window of about 35 minutes with at least one fitting activity; waits under 10 minutes and very long waits score lower. |
| Nighttime comfort | 10% | Observable signals that matter after dark. |
| Walkability | 5% | How easy it is to get around on foot from the charger. |
| Basic needs | 5% | Things like restrooms. |
In this model an activity only counts as a fit if you can walk there, spend a reasonable time, walk back and still keep a buffer of at least 5 minutes, or 20 percent of the charge window if that is longer. It measures against the short end of the charging estimate, because coming back a few minutes early is better than leaving a full car blocking a stall. Places that close before you would be back are left out, and if nothing fits, the stop is flagged as having no fitting activity rather than being given a poor match.
Each score carries a confidence label based on how complete the underlying data is: high when at least 80 percent of the inputs are known, limited from 50 percent, and low below that.
What we deliberately do not do
We do not compute a "safety score" from crime statistics. Scores like that tend to encode bias, give false reassurance, and steer people away from whole neighbourhoods. Instead the app shows observable signals and tells you how confident it is.
Limits worth knowing
- Charging times are estimates, not promises. Your car's own display is the final word during a session.
- Station listings can be out of date, and a listed charger can be broken or busy.
- Opening hours and place details come from third-party map data and can be wrong.
- Always plan enough range to reach a second charger if the first one does not work out.