Yacht Generators: How We Picked the Right System (Or Not)

Yacht Generators: How We Picked the Right System (Or Not)

What to do about yacht generators? We debated this topic for longer than expected, because we didn’t simply want a generator; we wanted to understand energy management onboard the vessel. What uses energy, what produces it, and how do these systems behave at anchor, underway, and in the marina?

It turns out the answer was not as straightforward as simply choosing a standalone generator.

Solar as Part of Yacht Generator Strategy

Hull No. 1, Mobius, uses a pure battery-based system: solar, shore power, and main engines feed into the batteries, and everything else draws from them.

Hull No. 2, Vanguard, is different.

Our two main engines use standard John Deere alternators, but they can only deliver around 3 kW/hour each, far too little for serious charging. FPB vessels add additional alternator capacity, but even then, diesel engines dislike long periods of low-load operation, which is inevitable during charging.

We also have an 8 kW solar array on the cabin roof. Brilliant in bright sun, zero at night, and reduced at high latitudes. Useful but not continuous.

How Battery Type Influences Yacht Generator Choices

Battery chemistry plays a major role in whether traditional yacht generators are even necessary:

• Lead Acid – Slow to charge, must reach full charge for longevity

• Carbon Foam (Firefly): Faster charging, better tolerance for partial state of charge

• Lithium (LiFePO₄) – Can accept high charge rates, ideal for rapid replenishment

Lithium is the game-changer here. With lithium, if you have a large power source, you can dump energy into the batteries rapidly, then rely on battery output for extended periods.

But this led us to rethink what a “generator” truly is.

Hybrid Yacht Generators: Using the Main Engines for Power

We chose a hybrid diesel-electric drive. Initially, we selected 20 kW electric motors for maneuvering. However, with 2 × 60 kWh battery banks, a full charge would take over 3 hours.

So we increased the hybrid motors to 30 kW, which dramatically speeds up charging.

Now the crucial discovery:

A 30 kW electric motor at 300 RPM becomes ~90 kW of electrical output at 2500 RPM.

An AH-HA moment indeed.

This meant:

• The hybrid motors must be sized not for propulsion,

• but to match battery charging requirements.

This charging strategy requires lithium, and yes, it creates a potential single point of failure (a topic for another post), but the benefits are substantial.

Yacht Generator Alternatives: Do We Even Need Them?

Our energy system eventually looked like this:

• Underway – Engine and hybrid motor provide unlimited electrical power

• In a marina, shore power is abundant

• At anchor—Large house + hybrid battery banks supply energy

• Daily engine run—~30 minutes to recharge the hybrid and house batteries

• Solar—tops up batteries whenever conditions allow

With this setup, the question naturally emerged:

Why install one or even two traditional yacht generators?

With:

• Large lithium battery capacity

• High-output hybrid charging

• Solar topping up

• Redundant power generation via two main engines

We concluded:

We don’t need conventional yacht generators at all.

And the result?

A quiet, low-vibration, peaceful experience at anchor with full redundancy.

Read Also

• Preparing for Vanguard Launch Day

• Explorer Yacht Electrical System Design

• Building Vanguard