Solar electric boat

What it means

A solar electric boat carries photovoltaic panels that charge the battery from daylight. On most boats the array supplements the battery; on a few, with enough deck area and a slow enough cruising speed, it can meaningfully extend range or even sustain it.

What the numbers really give you

Solar is quoted in peak watts — a 2 kW array, say. Peak means full midday sun, panels clean and flat to it, which no boat achieves for long. A realistic European day yields perhaps four to five times the peak figure in watt-hours across the whole day, less in spring and autumn, much less under cloud. Against a 40 kWh battery, that is a useful trickle rather than a refill.

Why it matters

Solar is at its most valuable at anchor, where it runs the fridge and the lights and keeps the boat self-sufficient for days without shore power. Judged as a way of making a fast boat go further it usually disappoints; judged as autonomy at rest it often exceeds expectations.