Scenario analysis
Which GPS watches survive the UTMB?
None of them, on a single charge. No watch we tested holds the 46.5-hour UTMB cut-off under continuous multi-band GPS in a cold alpine night. So the useful question is not which watch survives, but how far each one gets before blackout and how often you have to charge on the move.
The modelled conditions
These are the UTMB scenario inputs, chosen to represent an exposed alpine night. They are modelled conditions and chosen inputs, not a field measurement.
- Ambient temperature: 0 °C
- Wind: 6 m/s
- Cut-off window: 46.5 h (official UTMB limit)
How far each watch gets
| Device | Claim (h) | Blackout ETA (h) | Window coverage | Reality gap |
|---|---|---|---|---|
| Fenix 8 51mm Solar Sapphire Garmin | 84h | 14.4 | 31% | 82.8% |
| Fenix 7X Solar Sapphire Garmin | 89h | 12.6 | 27% | 85.9% |
| Enduro 3 Solar Sapphire Garmin | 60h | 19.8 | 43% | 66.9% |
| Vertix 2S Coros | 43h | 16.3 | 35% | 62.0% |
| Apex 2 Pro Coros | 75h | 16.3 | 35% | 78.3% |
| Vertical Titanium Solar Suunto | 60h | 14.6 | 31% | 75.7% |
What that means on the route
- Fenix 8 51mm Solar Sapphire: blackout around hour 14, well short of the 46.5h finish.
- Fenix 7X Solar Sapphire: blackout around hour 13, well short of the 46.5h finish.
- Enduro 3 Solar Sapphire: blackout around hour 20, well short of the 46.5h finish.
- Vertix 2S: blackout around hour 16, well short of the 46.5h finish.
- Apex 2 Pro: blackout around hour 16, well short of the 46.5h finish.
- Vertical Titanium Solar: blackout around hour 15, well short of the 46.5h finish.
Field validation: none yet
These cold and high-wind conditions are physically modelled but not independently field validated, the same status the methodology page states for the extreme-cold tail of the curve. The figures are model output under one fixed scenario, not measured runtime, and we make no stronger claim here than on any device dossier.
Why only these six
This page covers only the six devices whose display power is traced from documented sources. The AMOLED watches added later share a single baseline display figure rather than per-device measurements, so publishing scenario numbers for them would rest on an unsourced placeholder. We leave them out until that input is sourced.
Audit your own route to see where a specific device blacks out on your GPX, segment by segment.
DATASET · HIKINGSPECS LAB · FORMULA v1.0 · CC BY 4.0
Physics-derived estimate under one fixed reference scenario. The model is calibrated but not yet independently validated against measured field runtime. Estimated hardware inputs are labeled as such. Full method at /methodology.