Diagnosis & Decision 11 min read May 30, 2026

Nomad autonomy score: how to assess a van or sailboat before you buy

Q: Why assess a van's autonomy BEFORE buying?

Because 60 % of fast resales (<18 months) are tied to energy or water undersizing that makes real-world use impossible. A 2-hour pre-purchase audit typically avoids 5,000–12,000 € of retrofit.

Q: What are the key indicators to check?

Four: usable battery capacity (LiFePO4 Ah × depth of discharge), installed solar power vs Wh/day consumption, drinking-water volume vs target autonomy duration, and a heating system compatible with the intended season.

Q: Is the score valid for a sailboat too?

Yes, with adjusted weightings: wind generation and a hydrogenerator come into play, the water criterion replaces daily autonomy with passage autonomy, and satellite/SOS safety gains weight.

Buying a converted van or sailboat is a 25,000 to 180,000 € investment. Yet the vast majority of buyers judge on looks and mileage, not on the real ability to sustain the intended use. A diagnostic framework.

axes of the Nomad score

60 %

resales <18 months tied to undersizing

5–12 k€

retrofit avoided by a pre-purchase audit

0–100

score scale

Nomad scoring: 4 axes, not 1

• Onboard energy — sustainable usable kWh/day (battery × DOD ÷ usage), solar capacity vs target region.
• Water — autonomy in days by profile (sedentary 2d vs roaming 7d), filtration available.
• Safety & connectivity — SOS system, satellite, navigation redundancy.
• Route fit — heating / cooling consistent with targeted seasons + latitudes.

See also the Home counterpart of the score, which shares the same data-sovereign philosophy.

5 questions to ask the seller first

1. What is the batteries' real usable capacity (Ah × effective DOD)?

A 200 Ah lead-acid battery at 50 % DOD = 100 Ah usable. A 200 Ah LiFePO4 at 90 % DOD = 180 Ah usable.

2. What is the measured solar output in winter vs summer?

The underestimated ratio is typically 1:4 between December in Lille and June in Marseille. Ask for the historical MPPT log.

3. What is the drinking-water volume + the filtration system's flow rate?

Beyond 100 L onboard, check the tank's position (weight, frost insulation).

4. Is the heating sized for the intended season?

Webasto/Espar 2 kW = limit at -5 °C. Below that, plan for 4 kW or reinforced insulation.

5. What emergency communication system is on board?

Phone alone = insufficient out of coverage. inReach Mini 2 or Zoleo recommended when roaming.

Reading the score: 3 decision bands

0–40 — Purchase not recommended

Structural undersizing. The retrofit often exceeds the initial purchase savings.

40–70 — Quantified negotiation

Acquisition possible with a costed retrofit budget deducted from the price. The Nomad report lists the actions and costs.

70–95 — Ready for intended use

Acquisition validated for the tested scope. Caveat: a change of use (season, latitude) requires re-scoring.

À retenir

The Nomad score assesses 4 axes — onboard energy, water, safety & connectivity, route fit — on a scale of 0 to 100.
Real usable capacity: a 200 Ah lead-acid battery at 50 % DOD yields only 100 Ah usable, versus 180 Ah for a 200 Ah LiFePO4 at 90 % DOD.
Solar output varies by roughly 1:4 between December in Lille and June in Marseille: require the historical MPPT log before buying.
A Webasto/Espar 2 kW heater tops out around -5 °C; below that, plan for 4 kW or reinforced insulation.
Three decision bands: 0–40 no purchase (the retrofit exceeds the purchase savings), 40–70 quantified negotiation, 70–95 ready for intended use — a pre-purchase audit saves 5–12 k€ in retrofit.

FAQ

Why assess a van's autonomy BEFORE buying?