Top speed and cruising speed

What they mean

Top speed is the fastest the boat will go, briefly, in ideal conditions. Cruising speed is the pace it is designed to hold for hours. Both are quoted in knots — one knot is one nautical mile per hour, about 1.85 km/h.

Why the gap is wider on an electric boat

Power required rises far faster than speed. Adding a few knots at the top of the range can double or triple the draw, so a battery that supports six hours at cruising speed may support forty minutes flat out. A combustion boat has the same physics but a fuel tank that hides it; on an electric boat the consequence is immediate and visible.

What it looks like in numbers

Three boats in this catalogue show the shape of the gap. The Axopar AX/E 22 tops out at 36 knots, but its builder's own range figures are 60 nautical miles at 5 knots and roughly 17 at 25 — the same 63 kWh battery, eight times apart. The Crooze EZ 28 is quoted at 30 knots top and 12 cruising, with its 120 nautical miles measured at 5 knots. And the Elvene Amber, a solar-electric day boat, has a 15-knot top speed, a 9.5-knot cruise and 100 nautical miles at 5 knots on a 22 kWh pack — the smallest battery of the three and the longest published range, because the speed it is measured at is low. Read any range against the speed beside it, or not at all.

Why it matters

Top speed sells boats and cruising speed describes them. Plan a passage on the cruising figure, and only trust a range that names the speed it was measured at. Where a builder publishes a top speed but no range at all, the specification sheet is telling you which number it would rather you looked at.