How many kW does a sailboat need for electric propulsion?

If you’re repowering a sailboat with electric propulsion, the most common mistake is choosing motor power like you would for a car: “bigger is better.”

For most sailboats, the goal isn’t top speed. It’s reliable auxiliary power:

• docking and maneuvering
• motoring out of the harbor
• making steady progress in light air
• pushing into chop when you must

That usually lands in a small set of power “buckets”: 6 / 8 / 10 / 15 / 25 kW.

Best next step: use the free configurator to size your system and get a vendor-ready spec sheet.
→ Start here: /electric-boat-spec

Rule of thumb (quick answers)

These are typical ranges for monohull sailboats used as auxiliary power:

• 6 kW: small sailboats, light displacement, slow cruising (often 4–5 kn)
• 8 kW: common for ~28–33 ft boats as a “good enough” auxiliary
• 10 kW: common for ~33–40 ft boats or heavier displacement
• 15 kW: heavy monohulls, stronger headwinds/chop needs, frequent motoring
• 25 kW: large/heavy boats, high maneuvering authority, or fast multihulls

But speed matters more than people think.

The real driver: desired speed (knots)

Power demand rises slowly at low speed and very steeply as you approach hull speed (for displacement boats). That means:

• If you’re happy cruising at 4–5 kn, required kW stays modest.
• If you insist on 6–7 kn on a typical monohull, required kW can jump dramatically.

That’s why electric sailboat repowers often feel “underpowered” on paper:
people expect diesel-like thrust at hull-speed without paying the power/current cost.

A practical way to choose a kW bucket

Use these steps:

1) Decide your “normal” motoring speed

Most auxiliary use cases are:

• 4–5 kn (conservative, efficient, quiet)
• 5–6 kn (more capable, more power cost)
• 6+ kn (often expensive in batteries, current, and controller size)

2) Consider displacement and sea-state reality

Heavier boats need more power at the same speed. So does:

• chop
• headwind
• fouled bottom
• a less efficient prop setup

3) Choose a bucket with margin

If your required power is near your bucket at your target speed, you have little margin for conditions.

Example guidance (common setups)

30–34 ft monohull (typical cruiser)

• often lands around 8–10 kW
• with short bursts (maneuvering) needing more current than “cruise”

35–40 ft monohull (heavier cruising)

• often lands around 10–15 kW
• especially if you want 5.5–6 kn in chop

Multihulls

Multihulls can be very efficient at moderate speeds—but many owners also want higher speed. If you target higher speed, power grows fast.

Don’t forget: kW is only half the sizing problem

Choosing “10 kW” is easy. The expensive part is what it implies:

• Battery DC current (amps) at minimum voltage
• Controller/inverter phase current (RMS)
• Battery kWh for your runtime
• Charge time for your charger power

That’s why the spec generator outputs:

• recommended DC current rating
• recommended phase current rating
• kWh and Ah targets
• a performance curve (speed vs kW)

→ Generate your own spec: /electric-boat-spec

FAQ

Is 6 kW enough for a sailboat?

For small/light boats and conservative speeds (4–5 kn), yes. For heavier boats or pushing into chop, it can feel weak.

Is 10 kW enough for a 40 ft sailboat?

Sometimes, if you accept moderate speed and plan for conditions. Many heavy 40 ft cruisers feel better around 15 kW.

Why do electric systems “need” so much current?

At 48V-class systems, power translates into high current. More current means thicker cables, bigger fuses/contactors, and stricter thermal management.

Bottom line

Pick your target speed first, then choose the smallest kW bucket that gives you margin.

If you want a concrete, vendor-ready answer in minutes:

→ Start the configurator: /electric-boat-spec