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Electric boat calculator: range and licence

Think of it as the range calculator you know from electric cars, built for the water. Enter your usable battery capacity, the power your motor draws at cruising speed and how fast you go, and the electric boat calculator shows your running time, your range and where to turn around. The second part checks whether your motor needs a licence on German waters. Nothing you type leaves your browser.

Work out your range

Do I need a licence in Germany?

This calculator is an aid to planning, not legal advice. What counts is the wording of the regulations, the manufacturer's data and, if in doubt, what the competent authority tells you.

How the electric boat calculator works

Running time is the usable energy in the battery divided by the power the motor draws at cruising speed. Multiply by speed and you have the range. The reserve comes off first, and how big it is is up to you: we found no official or scientific recommendation for electric boats.

Usable capacity is not always the full rated capacity. How deeply a battery may be discharged is in the manufacturer's data sheet, and that is the figure to enter.

Going slower pays off. A rule of thumb from commercial shipping says propulsion power rises with the cube of speed: 10 per cent less speed cuts power by about 27 per cent and energy per distance by around 19 per cent. The study itself notes that this does not hold for every hull shape, so the table in the calculator is a guide.[1]

At a Froude number of about 0.4 the wave a vessel makes is roughly as long as the vessel, and wave resistance rises so sharply that displacement hulls can hardly get past it. From this we derived the value 2.43 times the square root of the waterline length in metres, giving knots.[2]

Licence rules for electric boats in Germany

On German inland and maritime waterways an electric boat needs no licence if its motor delivers no more than 7.5 kW in duty type S1, continuous operation under DIN EN 60034-1. For combustion engines the limit is 11.03 kW.[3]

No licence does not mean no age limit: on inland waterways the helmsperson must be at least 16, the only exception being boats without an engine. The German powerboat licence itself is also available from 16.[4][5]

The 7.5 kW limit applies on the Rhine too. Since April 2023 the Rhine crew regulations only require a sport patent for vessels between 20 and 25 m long.[6][7]

Lake Constance is stricter: above 4.4 kW you need a boatmaster's licence, electric motors included, and category A is only issued from 18. Every motorised boat there has to be registered.[8][9]

Renting? With a charter certificate from the rental company you may skipper boats under 15 m without a licence, but only on certain inland waterways, only boats with fixed berths and at no more than 12 km/h.[10][11]

Charging and batteries on board

German waterway signs include an order to use shore power at a mooring (B.12) and a notice that a shore power connection is available (E.25). Where B.12 is posted, a moored vessel must draw all its power from shore. We found no official list of such points for recreational boats. Waterway signs explained[4]

The register of charging points kept by the Federal Network Agency does not help either: it lists public charging points for electric vehicles, but moorings with shore power are not a category of their own.[12]

For charging, the German loss prevention institute IFS advises: use only the charger supplied, keep it dry, at room temperature, on a non-flammable surface and with a smoke alarm, and never leave it charging unattended overnight. A damaged or dropped battery should not be used again or taken apart.[13]

If a lithium-ion battery catches fire, German fire brigade associations recommend water as the extinguishing agent: cool early and for a long time, and keep watching the heat afterwards.[14]

For winter storage, charge the battery to 30 to 60 per cent and keep it dry at 10 to 20 degrees Celsius. Leaving it fully discharged for long periods damages it.[15]

Frequently asked questions

How far can an electric boat go on one charge?

Divide usable battery capacity in kWh by the power draw in kW to get running time in hours, then multiply by speed. With 10 kWh, 4 kW and 5 knots that is 2.5 hours and 12.5 nautical miles without a reserve.

Up to how many kW is an electric boat licence-free in Germany?

Up to 7.5 kW continuous power in duty type S1 on German inland and maritime waterways. On Lake Constance a boatmaster's licence is needed above 4.4 kW.

Does continuous or peak power count?

For the 7.5 kW limit it is the continuous S1 rating. For the 4.4 kW on Lake Constance the rules do not say explicitly.

How much reserve should I keep in the battery?

There is no official recommendation. The slider starts at 20 per cent, which is not a recommendation; set it yourself according to the water, the weather and the current.

More for boaters

Waterway signs explained Boating licence academy Boat trailer towing calculator Boat safety check planner

Sources

Legal position as of 12 October 2026, all sources retrieved that day.