How to Choose a Solar System for Your Yacht?

Solar power on boats has stopped being a fashionable add-on and become a serious part of the energy system on a modern yacht. More and more owners of motor yachts, sailboats and catamarans want to spend longer stretches at anchor without running the generator, without depending on a shore-power connection in the marina, and without the unpleasant noise and vibration that spoils the quiet of a cove. Solar panels make that possible — but only if the system is properly designed.

• How to choose a solar system for your yacht? A yacht’s solar system is chosen according to the vessel’s real daily electricity consumption, the surface area available for panels, and the capacity of the battery bank. First you calculate daily consumption in Wh, then estimate the realistic solar output for the waters you cruise, and finally you match panel power and battery capacity to that consumption, with a sensible reserve.

Why solar power matters more and more on modern vessels

A modern yacht uses far more electricity than a boat did twenty years ago. Refrigeration, large chartplotters, radar, autopilot, LED lighting, pumps, cabin fans, phone and laptop chargers, and — increasingly — an inverter to run 230 V appliances all add up to a constant draw that has to be covered somehow while you’re away from shore power.

The classic answer was a generator plus charging the batteries off the main engine. Both still have their place, but both mean noise, fuel consumption and maintenance. A solar system runs silently, with no moving parts and no fuel, and it charges the batteries exactly when you’re spending the most time outdoors — anchored in good weather.

It’s important, though, to set realistic expectations from the start. A solar system can significantly reduce the need for a generator and increase a vessel’s energy autonomy, but only if it’s correctly sized. An oversized system means wasted money and wasted space; an undersized one leaves you with flat batteries in the middle of the weekend. The real value of solar power on a yacht lies in carefully matching generation, consumption and storage.

What is a solar system on a yacht?

A solar system on a boat is not just a panel on the roof. It’s a complete assembly of several components that have to work together:

Solar panels convert sunlight into direct-current (DC) electricity. Their power is expressed in watts (W) — more on that below. Panels are the most visible part of the system, but not the most important on their own.

The solar charge controller sits between the panels and the batteries. Its job is to turn the voltage and current coming from the panels into a form suitable for safely charging the batteries, and to prevent overcharging. There are two basic technologies — PWM and MPPT — which we cover in a separate section.

The battery bank stores the energy produced so it can be used when the sun isn’t shining — at night, in cloudy weather, or whenever consumption exceeds the current output. Battery capacity is often the real bottleneck of the system, more so than panel power itself.

The inverter converts the batteries’ DC voltage (usually 12 V or 24 V) into the 230 V AC needed for household appliances such as a microwave, a coffee machine or a laptop charger. Not every vessel needs an inverter, but where there is one it has a major impact on consumption.

Cabling, fuses and protection make up the part of the system that’s easiest to underestimate. Cable cross-section has to be large enough to carry the current without overheating or voltage drop, and fuses and isolators protect the system against faults and fire. Poor wiring can ruin even the best panel.

System monitoring — usually through a battery monitor or the controller’s app — lets you see at any moment how much energy is coming in, how much is going out, and how much is actually left in the batteries. It’s the tool you can’t really manage energy without over the long run.

Basic concepts: the difference between W, Wh, kWh, A and Ah

Before any calculation, you need to understand a few basic units, because this is exactly where most of the confusion happens.

A watt (W) is the unit of power — how much energy a device draws or produces at a given moment. A 400 W panel has a rated power of 400 W; a fridge draws maybe 50 W while its compressor is running.

A watt-hour (Wh) is the unit of energy — how much power is consumed or produced over time. A 50 W device running for 10 hours uses 50 × 10 = 500 Wh. This is the most important unit for sizing, because it describes actual daily consumption.

A kilowatt-hour (kWh) is simply a larger unit of energy: 1 kWh = 1000 Wh. The daily consumption of a larger yacht is easier to express in kWh (e.g. 3000 Wh = 3 kWh).

A volt (V) is the system voltage. Marine DC systems most often run at 12 V or 24 V.

An amp (A) is the current, and an amp-hour (Ah) is the unit of battery capacity that’s most commonly quoted. Ah and Wh are linked by voltage: Wh = Ah × V. A 100 Ah battery at 12 V holds 100 × 12 = 1200 Wh, or 1.2 kWh of nominal energy.

Remember one equation and half the job is done:

• power (W) × running time (h) = energy consumed (Wh)

How to calculate how much electricity a yacht uses

This is the first and most important step. When choosing a solar system for a yacht, it isn’t enough just to look at how many watts the panels have. The first step should always be to estimate the vessel’s real daily electricity consumption.

In practice, owners often overestimate how much energy solar panels can produce and underestimate how much the fridge, navigation, electronics, lighting, inverter and other devices actually draw. That’s why we start from consumption, not from the panels.

1. List your electrical loads

Write down every device that draws power from the ship’s batteries. Typical loads on a yacht are:

• fridge and (if fitted) freezer
• navigation electronics: chartplotter, GPS, radar, VHF, AIS
• autopilot
• LED lighting (interior and exterior)
• pumps (bilge pump, pressurised freshwater pump, shower sump pump)
• fans
• TV and audio system
• chargers for phones, tablets and laptops
• the inverter and the 230 V appliances it powers
• other devices (air conditioning, watermaker and similar on larger vessels)

2. Estimate daily running time

Consumption depends not only on a device’s power, but also on how long it runs. Lights might be on for three hours in the evening, while the fridge runs all day — but its compressor cycles on and off, so it effectively runs only part of the time. For each device, estimate a realistic number of running hours per day.

3. Calculate each device’s daily consumption

For each device, multiply power by running time:

• device power (W) × running time (h) = consumption (Wh)

For example, three LED lights totalling 15 W that burn for 4 hours use 15 × 4 = 60 Wh.

4. Add up total daily consumption

The sum of all the individual figures gives you total daily consumption in Wh. That number is the foundation of the whole project. If it’s more convenient, convert it to kWh by dividing by 1000.

• How to calculate a yacht’s daily electricity consumption? For each device, multiply its power in watts by the number of hours it runs per day to get its consumption in watt-hours (Wh). The sum of all the devices gives you total daily consumption. That figure in Wh is the starting point for sizing your solar panels and batteries.

Which devices on a yacht use the most energy?

As a rule, the biggest energy users are the devices that run for a long time or continuously, not those with the highest instantaneous power. Refrigeration is almost always the single largest load, because it runs day and night. It’s followed by the autopilot on longer passages, the inverter with its 230 V appliances, and the navigation electronics. With LED technology, lighting is a relatively small load today.

How to estimate real solar output

This is where the most common mistake lies. A solar panel’s rated power is not equal to the amount of electricity the panel will produce over the course of a day. A panel rated at 400 W delivers 400 W only under ideal laboratory conditions — perpendicular sun, a clean panel, the specified temperature. In the real world it produces less, and only for part of the day.

For a rough estimate of daily output, the concept of peak sun hours is used — a figure that captures how many hours a day a panel effectively works as if at its full rated power. That figure depends on a number of factors:

• the number of sunny hours and the time of year — in summer on the Adriatic, output is far higher than in winter
• geographic location — the more sun, the better
• temperature — panels, paradoxically, lose efficiency when they get very hot
• shade — even a small shadow from the mast, rigging or a bimini frame can cut output disproportionately
• panel orientation and tilt — panels lying flat on a yacht’s roof are practical, but they don’t catch the sun optimally throughout the day
• system efficiency — losses in the controller, in the cables and during battery charging further reduce the usable energy

Because of all this, by way of illustration, a 400 W panel on a summer day in the Adriatic will realistically produce considerably less than its theoretical 400 W multiplied by the 12 hours of daylight. That’s why practitioners work with an effective number of peak sun hours (often on the order of a few hours a day, depending on conditions) and factor in system losses. The exact figure varies from vessel to vessel and from day to day, so any specific calculation should be treated as an estimate, not a guaranteed value.

How many solar panels does a yacht need?

There’s no universal answer. The number of panels a yacht needs cannot be determined by the size of the yacht alone. Two yachts of the same size can have completely different needs: one doing weekend trips with frequent marina hook-ups, the other on week-long cruises at anchor with refrigeration and an inverter running constantly.

The number of panels you need depends directly on three things: how much energy you use per day (Wh), how much you can realistically produce per watt of installed power at your location, and how much surface area you have available. The logic is simple: the installed panel power must, after real losses, produce at least as much energy as you use each day — and usually a little more, as a reserve and for cloudy days.

• How many solar panels does a yacht need? Enough that their realistic daily output covers the vessel’s daily consumption, with a reserve. The number isn’t set by the length of the yacht but by the calculated consumption in Wh, the estimated solar output for your cruising area, and the surface available for mounting. A small vessel with modest consumption may be happy with a single panel, while a larger motor yacht will need several hundred to more than a thousand watts.

How to size solar panels correctly — step by step

Let’s condense the entire sizing process into a logical sequence. This is a methodology worth applying to any vessel:

• List all your loads and their power ratings.
• Estimate the running time of each device over a typical day.
• Calculate daily consumption (W × h) for each device and add them up into total consumption in Wh.
• Estimate realistic solar output per watt of installed power for your location and cruising season, taking into account losses, shade and orientation.
• Determine the required panel power so that the estimated output covers consumption with a reserve.
• Size the batteries according to consumption and the number of days of autonomy you want.
• Build in a reserve — never design a system right at the edge of consumption.

The best solar system isn’t necessarily the one with the highest installed power, but the one that’s properly matched to consumption, batteries and the space available on the vessel.

How to choose your battery bank capacity

Panels produce energy during the day, but a vessel also consumes it at night. The batteries are the reservoir that bridges those two rhythms, and their capacity is often decisive for real autonomy.

Here it’s essential to distinguish a battery’s nominal capacity from its actually usable energy. No battery should be run down to zero. With conventional lead-acid batteries (AGM, gel) it’s reasonable to use only about half the nominal capacity without shortening their service life. Lithium-ion batteries — in practice most often LiFePO4 (lithium iron phosphate) — tolerate much deeper discharge, are lighter and last longer, so they deliver more usable energy from the same nominal capacity — but at a higher upfront cost.

That means a battery with a nominal 100 Ah (1.2 kWh at 12 V) in a lead-acid version realistically delivers about half that energy, while a LiFePO4 battery of the same nominal capacity delivers a much larger usable share. That’s why capacity is always sized according to usable, not nominal, energy.

Rule of thumb: the battery bank should cover at least one full day of consumption when there’s no sun, and preferably more if you cruise in areas and seasons with changeable weather.

• How much battery capacity does a yacht need? The battery bank should store at least one full day of the vessel’s consumption in usable energy, and preferably a reserve for cloudy days. It’s calculated from actually usable energy, not from nominal capacity, because lead-acid batteries are only discharged to about half while LiFePO4 can go much deeper.

The MPPT controller — what it is and why it matters

A charge controller is a mandatory part of every solar system. Without one, the panels could overcharge and damage the batteries. There are two technologies, and the difference between them directly affects how much energy you actually get.

A PWM controller (pulse-width modulation) is simpler and cheaper. It connects the panels and batteries by pulling the panel voltage down to the battery voltage, but in doing so part of the panel’s potential is lost, especially when the two voltages differ significantly.

An MPPT controller (Maximum Power Point Tracking) is a smarter device. It constantly seeks the panel’s optimal operating point and converts the excess voltage into additional charging current. In practice that means noticeably more usable energy from the same panels, particularly at lower temperatures, in partial cloud, and when the panels are wired to a higher voltage.

• What is an MPPT controller? An MPPT controller is a solar charge controller that tracks the panel’s maximum power point and converts excess voltage into additional battery charging current. Because of this, it extracts more energy from the same panels than a simpler PWM controller, especially in less favourable conditions. For a yacht’s solar system, MPPT is almost always recommended.

For any serious system on a yacht, MPPT is nearly always the better choice. PWM can make sense only for very small, simple systems where cost is the deciding factor.

Which solar panel to choose for a yacht

There’s no technology that’s always best — there’s the one that best suits your vessel and mounting method. Here are the relevant characteristics and the context in which each option makes sense.

Monocrystalline panels are the standard today because of their high efficiency, meaning a lot of power per unit of area. That matters on a vessel, where space is always tight.

Rigid panels in an aluminium frame with a glass surface are the most durable and longest-lasting, with the best efficiency and heat dissipation. They require a solid, flat base or a mount — ideal for a hardtop, an arch, or a fixed roof.

Flexible panels are thin and light and can be bonded to gently curved surfaces such as a bimini top or the coachroof. They’re practical and visually unobtrusive, but as a rule they have somewhat lower efficiency and a shorter service life than rigid panels, and because they’re bonded to the surface they dissipate heat less easily, which further reduces output on hot days.

When choosing, weigh up: efficiency, resistance to the marine (salt and damp) environment, weight, dimensions relative to the available area, sensitivity to shade, and ease of maintenance and cleaning. On a vessel with enough solid surface, rigid panels are usually the more cost-effective choice in the long run; where shape and weight are decisive, flexible panels solve a problem rigid ones can’t.

• Which solar panels to choose for a yacht? For most yachts, monocrystalline panels are chosen for their high power per unit area. Rigid panels last longer and are more efficient, so they’re the first choice where there’s a solid, flat surface (hardtop, arch). Flexible panels are lighter and fit curved surfaces such as a bimini, but they’re somewhat less efficient and shorter-lived.

Where to mount solar panels on a yacht

The mounting location determines two things: how much sun the panels catch and how much shade falls on them. Each possible location has its advantages and drawbacks.

The hardtop and the coachroof offer a large, flat and mostly shade-free surface — often the best spot on a motor yacht for rigid panels.

The bimini and other fabric covers suit flexible panels, since they’re curved and won’t bear the weight of rigid boards; they offer good exposure, but the panels run hot.

The superstructure and a stern structure (arch, davit, stern mount) make use of otherwise unused space and hold the panels up above the shade, but they require an additional structure.

A particular problem in every case is shade. A shadow from the mast, rigging, a radar mount, a bimini frame or even another panel can cut output disproportionately — on many panels, a single shaded cell drags the whole string down. That’s why panels should be placed where they are as unshaded as possible during peak daily sun, and for more complex layouts you should consider separate controllers or panels with technology that copes better with partial shade.

• Where is the best place to mount solar panels on a yacht? On the largest flat, unshaded surface — most often the hardtop, a stern arch, or the coachroof on motor yachts. The key is to avoid shade from the mast, rigging and superstructure, because even a small shadow can disproportionately reduce the output of an entire panel.

How shade, orientation and weather affect output

Three factors constantly reduce actual output compared with rated power, and it’s worth understanding them together.

Shade is the most insidious, because its effect isn’t proportional: ten percent of the surface in shadow doesn’t mean ten percent less energy, but often much more, depending on the panel’s design.

Orientation and tilt determine how perpendicularly the sun strikes the panel. Panels lying flat on a yacht’s roof are practical and catch the sun from all directions as the boat swings at anchor, but they aren’t tilted optimally toward the sun, so their output is lower than the same panel would deliver at an ideal tilt.

Weather is obvious, but easy to forget when planning: cloud, haze and dust on the panel reduce output — and it’s precisely for such days that the battery reserve exists. That’s why a system is never designed around the best possible day.

A solar system on a motor yacht versus a sailboat

Although the physics is the same, a motor yacht and a sailboat pose different challenges.

A motor yacht usually offers more large, flat and unshaded surfaces — hardtop, flybridge, coachroof — suited to rigid panels. There’s no mast or rigging casting shade. On the other hand, consumption is often higher: more refrigeration, more electronics, sometimes air conditioning and a higher-powered inverter.

A sailboat has a mast, rigging and canvas that create moving shade throughout the day, and the surface available for panels is usually smaller and more irregular. That’s why sailboats more often use flexible panels on the sprayhood or bimini plus stern mounts (an arch), and the question of shade carries even more weight.

• What’s the difference between a solar system for a motor yacht and one for a sailboat? A motor yacht has more large, flat, unshaded surfaces for rigid panels, but usually higher consumption too. A sailboat has less area and moving shade from the mast and rigging, so it relies more on flexible panels and stern mounts, and it’s more sensitive to the shade problem.

A solar system for a charter vessel

Charter vessels are a case of their own, because they’re used by a rotating cast of guests with the most varied habits. Some will save energy; others will keep the fridge full and the air conditioning on. Because of that unpredictability, a charter system is worth sizing to the upper end of consumption rather than the average, with a more generous battery reserve, robust and easy-to-use equipment, and clear battery-state monitoring. The goal is to reduce the number of situations in which a guest is left without power or the generator has to be started in the middle of the night.

Illustrative sizing examples

The following examples are hypothetical and simplified, purely to show the way of thinking. The figures are approximate and don’t represent the specification of any particular vessel or product. Your actual calculation will depend on your own devices and cruising habits.

Example 1 — a smaller yacht (illustrative)

Let’s imagine a modest daily consumption at anchor:

With a daily consumption of roughly 700 Wh, and given that realistic solar output is considerably lower than the rated figure, it’s reasonable to think about installed panel power on the order of a few hundred watts, so that on a sunny day it covers consumption and still charges the batteries. The battery bank should store at least one day of consumption in usable energy — so at least around 700 Wh usable, and preferably more for cloudy days. Again: the figures are illustrative.

Example 2 — a larger motor yacht (illustrative)

On a larger motor yacht, consumption rises because there are more devices and they run longer:

With a daily consumption of around 3 kWh, the requirement rises to installed panel power on the order of several hundred to over a thousand watts, depending on the available area and location, and to a considerably larger battery bank that covers at least a full day of consumption in usable energy. At this level of consumption, a solar system will often cover daily needs in sunny weather, but the generator or engine charging remain a top-up for cloudy days and peak loads. Here too, the figures are strictly illustrative.

Comparison table (indicative values)

The values in the table are indicative and illustrative, meant to convey the relationships between the categories, not as a universal standard. Actual needs depend on each vessel’s equipment and how it’s used.

Can a solar system replace the generator?

The answer is: it depends, and it’s worth being honest about the limits. At three different levels of ambition, the results differ.

As an auxiliary power source, a solar system is excellent and is most often used exactly this way — it covers the daily base load and you have to start the generator far less often.

As a primary power source, a solar system can serve on vessels with moderate consumption, enough panels and a solid battery bank, especially in summer. But a few cloudy days in a row, or unusually high consumption, is enough to make the reserve decisive.

Full energy independence with no other source is realistic only for vessels with very carefully limited consumption and a generous system — and even then it carries risk in bad weather. For most yachts, the realistic goal is for the solar system to drastically cut generator use, not to eliminate it entirely.

• Can a solar system replace the generator? For most yachts, a solar system doesn’t replace the generator entirely but takes a great deal of load off it. With moderate consumption, enough panels and quality batteries, it can cover daily needs in sunny weather, but the generator or engine charging remain a useful backup for cloudy days and peak loads such as air conditioning.

Can a solar system power the fridge, navigation and lighting?

Yes — these are exactly the typical loads a solar system covers every day. The fridge, navigation electronics, LED lighting and pumps make up the base load that a well-sized system handles easily. More demanding are high-instantaneous-power devices running through the inverter (air conditioning, cooktops, a water heater), which consume quickly and call for both stronger panels and stronger batteries.

How much can a solar system reduce generator use?

Honestly: it depends on your consumption, the system’s capacity, the season and how the vessel is used, so there’s no single percentage. On a vessel with moderate consumption and a well-sized system, the generator can be reduced to rare occasions in summer, while with high consumption and demanding loads the solar system covers the base and the generator remains for the peaks. A realistic expectation beats promising a specific number.

The most common mistakes when choosing a solar system

A few typical mistakes come up again and again in practice. Avoid them and you’ve avoided most of the disappointments:

• Buying panels by maximum power alone, without calculating consumption — the system ends up either oversized or poorly matched.
• Ignoring real daily consumption — without a figure in Wh, every choice is guesswork.
• Underestimating losses — a panel’s rated power is not its daily output; losses in the controller, cables and during charging are real.
• Neglecting shade — a single shaded panel can drag down an entire string.
• Sizing the batteries wrong — too small a bank, or working from nominal instead of usable capacity.
• Using the wrong controller — PWM where MPPT would use the panels far better.
• Cable cross-section too small — voltage drop and overheating waste energy and create risk.
• Lack of protection — a system without fuses and isolators is dangerous and non-compliant.
• Expecting full output all day long — output is concentrated around midday and changes with the sun.
  Ignoring real conditions at sea — salt, damp, vibration and temperature all affect the equipment and its output.

How much does a solar system for a yacht cost?

The price of a solar system depends too much on the specific vessel to be reduced to a single number, and quoting made-up figures would be irresponsible. Instead, it’s more useful to know which factors drive the cost, so you can understand the quote you receive:

• the number and type of panels and the total installed power
• the type and quality of the controller (MPPT is generally more expensive than PWM)
• battery capacity and technology (LiFePO4 costs more than lead-acid but lasts longer)
• whether there’s an inverter and how powerful it is
• installation and any additional structure (mounts, an arch)
• cabling, fuses and protection
• integration with the existing onboard system and its complexity

The most expensive part of a quality system is often not the panels but the batteries and a flawless installation — and that’s precisely where it doesn’t pay to cut corners.

How to choose a solar system for a new yacht

If you’re considering a new motor yacht, the energy system is best planned during the vessel’s configuration rather than afterwards. When electrical needs are defined in advance, the panels, batteries, controller and inverter can be chosen from the outset to work together, cable runs and mounting locations can be planned without later compromises, and expensive modifications down the line can be avoided. Thinking about consumption at the configuration stage simply gives you a cleaner, tidier and more reliable system.

Conclusion

Choosing a solar system for a yacht is at its core a technical decision, not a marketing one. The order is always the same: first calculate consumption, then determine the output you need, then match the batteries and the other components. A panel’s rated power is not the amount of energy you’ll get; shade, orientation and weather are real factors; and the batteries and a quality installation often decide satisfaction more than the sheer number of watts.

There’s no universal solar system that suits every yacht. There’s the one that’s properly sized to your vessel, your consumption and the way you cruise — and that’s exactly the kind of system that brings quiet at anchor, fewer generator starts, and more freedom on the water.

Checklist before buying a solar system

Before you make the decision, check:

• What is the vessel’s real daily consumption (in Wh/kWh)?
• How much surface is available for solar panels?
• How much shade falls on the panels during the day?
• What is the battery capacity — and how much of it is usable?
• Which controller do you use (MPPT or PWM)?
• Is there an inverter, and how much do the 230 V appliances draw?
• What is the total installed panel power?
• Are the cables of sufficient cross-section, and is the required protection in place (fuses, isolators)?
• How will the system be maintained and cleaned?
• What are the real conditions of use during the season (location, weather, cruising style)?

Frequently asked questions (FAQ)

How to choose a solar system for a yacht?

Start from your real daily consumption in Wh, estimate realistic solar output for your location, then match panel power and battery capacity with a sensible reserve. The size of the yacht in itself isn’t the measure — consumption and how it’s used are.

How many solar panels does a yacht need?

Enough that their realistic daily output covers daily consumption with a reserve. A small vessel with modest consumption may be happy with a single panel; a larger motor yacht will need several hundred to over a thousand watts of installed power.

How many watts of solar does a boat need?

It’s not set by a rule of thumb, but derived from consumption. Calculate daily consumption in Wh, estimate how much energy one watt of panel yields at your location (after losses), and arrive at the required installed power. That’s why two boats of the same size can need very different power.

Can a solar panel charge a boat battery?

Yes, but never directly without a controller. A solar charge controller (preferably MPPT) is mandatory between the panel and the battery; it adjusts voltage and current and prevents overcharging and damage to the battery.

What is an MPPT controller?

An MPPT controller tracks the panel’s maximum power point and converts excess voltage into additional charging current, so it extracts more energy from the same panels than a simpler PWM controller — especially at lower temperatures and in partial cloud.

What’s the difference between an MPPT and a PWM controller?

PWM is simpler and cheaper, but part of the panel’s potential goes unused. MPPT is more efficient because it optimises the panel’s operating point and delivers more energy. For any serious system on a yacht, MPPT is almost always recommended.

How long does a solar panel last on a boat?

Quality rigid monocrystalline panels are generally very long-lived and retain much of their power over many years, while flexible panels usually have a shorter life. Actual lifespan depends on panel quality, conditions and maintenance, so the specific figure should be checked in the manufacturer’s warranty and specification.

Are flexible solar panels good for yachts?

They are when low weight and mounting on curved surfaces such as a bimini or the coachroof matter. Their drawback is generally somewhat lower efficiency, poorer heat dissipation and a shorter life than rigid panels. Where there’s a solid, flat surface, rigid panels are usually the better long-term choice.

Where is the best place to mount solar panels on a yacht?

On the largest flat, unshaded surface — on motor yachts, most often the hardtop, flybridge or a stern arch. The key is to avoid shade from the mast, rigging and superstructure, because even a small shadow can disproportionately reduce output.

Can solar power run a fridge on a yacht?

Yes. The fridge is a typical load a solar system covers every day, but because it runs around the clock it’s often the single largest consumer. That’s why it should be factored in at the very start of sizing, with enough battery capacity for overnight running.

Can a solar system replace the generator?

For most yachts, a solar system significantly reduces the need for a generator but doesn’t replace it entirely. With moderate consumption, enough panels and good batteries it can cover daily needs in sunny weather, while the generator remains a backup for cloudy days and large loads.

How to calculate daily electricity consumption on a yacht?

For each device, multiply its power in watts by the number of hours it runs per day (W × h = Wh), then add up all the devices. The resulting figure in Wh (or kWh) is the starting point for choosing panels and batteries.

How much battery capacity does a yacht need?

Enough to store at least one full day’s consumption in usable energy, and preferably a reserve for cloudy days. It’s calculated from actually usable rather than nominal energy, because lead-acid batteries are only discharged to about half while LiFePO4 can go much deeper.