Range at a stated speed

What it means

Range is the distance a boat can cover on one charge — but the number only means something with a speed attached to it. Power consumption rises steeply with speed, so the same battery that gives 60 nautical miles at 5 knots may give 20 at 12. A range quoted without its speed is not a specification; it is a choice of the most flattering point on the curve.

How it is measured

Range is stated in nautical miles at a named cruising speed, derived from the usable capacity of the battery and the power needed to hold that speed. It assumes calm water, a clean hull and no headwind. All three cost range in practice, and none of them is in the brochure.

Why it matters

It decides whether a passage is possible at all. On a day boat the question is how many hours before charging; on a large catamaran it is whether a crossing can be attempted. It is also the figure a buyer can least easily verify, which is why we publish it only with the speed the builder stated it at.