Tesla Trip Buffer Planner
Updated .
This planner checks one leg of a trip. From the leg distance, your own consumption in Wh per mile or km, the starting charge and the pack size, it predicts the arrival percentage and compares it with the buffer you choose. It returns OK, tight or add a charging stop and shows every step of the arithmetic. The buffer is a personal choice, not a Tesla figure.
How it works
The planner uses five lines of arithmetic, each shown in the result:
- Consumption with allowance = your consumption × (1 + extra ÷ 100).
- Energy needed (kWh) = distance × consumption with allowance ÷ 1000.
- Energy at the start (kWh) = pack size × starting charge ÷ 100.
- Energy on arrival = energy at the start − energy needed, shown as a percentage of the pack.
- Margin = arrival percentage − your buffer, in percentage points.
The verdict rule is this tool’s own rule of thumb, not Tesla’s: a margin of 5 points or more is OK, a margin from 0 to under 5 is tight, and a negative margin means add a charging stop. If the stop is needed, the note says roughly how much energy would restore your buffer.
Choosing the extra percentage. Compare the consumption on a past trip in similar conditions with your usual figure: (past − usual) ÷ usual × 100. If your usual figure is 285 and the cold-weather trip showed 313.5, that is 10%. Use your own history rather than a guess. The car’s own trip planner uses its own model, so treat this tool as a second opinion you can check by hand, and see the road trip guide for how to set a buffer you trust.
Worked example
Suppose a leg of 140 miles, a consumption of 285 Wh per mile from the driver’s own trip screen, a start at 80%, a hypothetical 60 kWh usable pack, a 10% buffer and no extra allowance.
Energy needed: 140 × 285 ÷ 1000 = 39.9 kWh. Energy at the start: 60 × 0.80 = 48 kWh. On arrival: 48 − 39.9 = 8.1 kWh, which is 13.5% of the pack. Margin: 13.5 − 10 = +3.5 points, so the verdict is tight.
Now add a 20% allowance for a headwind. Consumption becomes 342 Wh per mile, the leg needs 47.88 kWh, and the arrival charge falls to 0.12 kWh, about 0.2%. That is 9.8 points under the buffer, so the verdict is add a charging stop, and roughly 5.9 kWh would restore the buffer. The same leg flips from workable to unworkable on one assumption, which is why it pays to enter your own conditions honestly. These numbers are illustrative arithmetic, not data for any Tesla model.
Frequently asked questions
Is the 10% buffer a Tesla recommendation?
No. It is a starting value you can change. The right buffer depends on your route, how well you know the chargers on it and the weather, so it is your decision.
Where do I get my Wh per mile or km?
From your own car’s energy or trip display, ideally from a similar recent trip in similar conditions. Names and locations differ between models and software releases, so check your owner’s manual.
What should I enter for headwind, cold or hills?
A percentage you estimate from your own past trips: compare consumption in those conditions with your usual figure. If you have no history, run the tool with a few values, such as 0, 10 and 20, and see how the verdict changes.
Does this replace the car’s trip planner?
No. It is a hand-checkable second opinion for one leg. The car’s own planner may account for things this tool does not, so use both and favour the more cautious answer.
What if the verdict is tight?
Treat it as a prompt to add a short top-up, slow down a little, or choose a closer charger. A tight result means any extra headwind or detour could remove your margin.
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