Solar installation on a yacht (panels, MPPT controller)
Energy balance, choosing panels and an MPPT controller, and a correct, safe solar installation.
Designing a solar installation starts with an energy budget, not with buying panels. Add up the daily consumption of every load in amp-hours (Ah) or watt-hours (Wh): fridge, lighting, navigation electronics, pumps, charging devices. Then estimate the realistic yield from the panels — in practice a panel delivers about 3–5 times its rating in Wh per day, heavily dependent on the season, the latitude and shading. Those two numbers give the panel power and the battery capacity you need.
Panels divide into rigid monocrystalline ones (the highest efficiency and durability, needing a rigid mounting) and flexible/semi-flexible ones (light, can be bonded to the deck, but usually with a shorter life and sensitive to overheating). The greatest enemy of the yield is shade — even the shadow of the boom, the backstay or a stanchion drastically reduces the current of the whole panel. Mount panels where the shade falls least often (on a stern arch or the bimini, for example), and consider splitting the array into several smaller panels with their own controllers.
The charge controller is the heart of the system. PWM controllers are cheap but only efficient when the panel voltage is close to the battery voltage. MPPT (Maximum Power Point Tracking) controllers track the maximum power point and convert the surplus voltage into current, usually giving 15–30% more energy, especially in the cold, under partial cloud and with higher-voltage panels. On a yacht you practically always choose MPPT. Size the controller for the panels' short-circuit current and the battery voltage, with a margin.
Choosing cable sections and protection is a safety matter. Size the cables between the panels and the controller and between the controller and the battery so that the voltage drop stays below about 3%, which on long runs means heavy cable. On the battery side, fit a fuse close to the battery positive (it protects against fire in a short circuit), and on the panel side use protection as the controller's documentation specifies. Use solar connectors (MC4 type) and UV-resistant cabling.
How the panels are connected affects how the controller works. Wiring in series raises the voltage (lower cable losses, better for MPPT in weak light), but shading one panel cuts the whole string badly. Wiring in parallel keeps the voltage low and is more tolerant of partial shading, but needs heavier cable. On a yacht deck full of shadows, several smaller panels with their own MPPT controllers are often better than one big series string.
Set the correct charging profile in the controller for the type of battery — AGM, gel and LiFePO4 have different absorption and float voltages. The wrong profile shortens the batteries' life or is downright dangerous. Modern controllers (Victron, for instance) let you monitor the yield and the state of the batteries over Bluetooth, which makes it easy to check the energy budget in practice. Check that temperature compensation of the charging is active or that a temperature sensor is connected.
The mechanical installation has to survive marine conditions. Mount rigid panels on a stainless steel or aluminium structure with ventilation underneath (cooling raises the output), and seal the cable passages through the deck with glands and polyurethane compound. Avoid running DC cables loose — secure them with ties and protect them from chafe. Once installed, measure the voltages and currents and confirm that the controller enters its charging stages. The Victron and Mastervolt documentation contains ready-made selection diagrams.
Material prices — products and options
Indicative prices in EUR (incl. VAT), as of July 2026. Products widely available in Europe; prices depend on the shop, the pack size and consumption. The links lead to example shops that ship across the EU. Dollar amounts are converted at 1 EUR = 1.1622 USD (ECB, 7 September 2026) and rounded — treat them as a rough guide, not a price in a US shop. Imperial values in brackets are conversions of the metric figure.
Rigid monocrystalline photovoltaic panels
- Offgridtec — rigid mono panel 100–120 W
budget 12 V module, aluminium frame, ~100 W€90–140 (≈$105–163) - Victron — BlueSolar Mono 115 W / 12 V
rigid panel with an IP65 junction box, 25-year power warranty€90–120 (≈$105–139) - Victron — BlueSolar Mono 175 W / 12 V
1485×668×30 mm (1.18 in), 11 kg (24.3 lb), efficient in low light€120–160 (≈$139–186)
Flexible panels (semi-flex, on the bimini / deck)
- Offgridtec — ETFE-AL 100 W V2 semi-flex
budget flexible ETFE panel, mono cells, ~100 W€110–150 (≈$128–174) - Solara — Power M-Series S560M43 140 Wp (walk-on)
semi-flexible marine module made in Germany, can be walked on€380–500 (≈$442–581) - Solbian — SR Super Rugged ~100–120 W
premium, SunPower cells at ~24%, for the sprayhood / bimini, ~2 mm (0.08 in)€390–460 (≈$453–535) - Solbian — SP Sun Power Maxeon ~130–150 W
back-contact, up to 25% efficiency, 150 W for only ~2 kg (4.4 lb)€430–560 (≈$500–651)
MPPT charge controller
- Victron — SmartSolar MPPT 100/20
Bluetooth, up to 20 A / 100 V, up to about 290 W (12 V)€90–110 (≈$105–128) - Victron — SmartSolar MPPT 100/30
Bluetooth, up to 30 A / 100 V, up to about 440 W (12 V)€120–140 (≈$139–163) - Victron — SmartSolar MPPT 100/50
Bluetooth, up to 50 A / 100 V, larger arrays€170–200 (≈$198–232) - Votronic — MPP 350 Duo Digital
German MPPT, charges two banks (starter + service)€180–240 (≈$209–279)
UV solar cable + MC4 connectors
- Seatec — 6 mm² solar cable with MC4 connector (by the metre)
UV resistant, ready-made MC4 ends / open ends, price per metre€8–30 (≈$9–35) - Seatec — set of male/female MC4 connectors 4–6 mm²
pair of plugs for fitting the cable yourself€3–6 (≈$3–7) - Seatec — MC4 Y-splitter 2-to-1 / 300 mm (11.81 in)
connecting two panels in parallel€10–14 (≈$12–16)
DC fuses / breakers + fuse holders
- Blue Sea — in-line ATO fuse holder
cheap in-line holder for a low-current solar circuit€11–15 (≈$13–17) - Blue Sea — MRBF Terminal Fuse Block, 10 mm (0.39 in) / M8 hole
fuse mounted on the battery terminal€32–48 (≈$37–56) - Blue Sea — ANL AK2 fuse block / up to 300 A
for the main circuit / larger battery banks€35–48 (≈$41–56) - Victron — MEGA fuse + holder
main fuse for 12/24 V installations€20–45 (≈$23–52) approx.
Mounting structure (stainless / aluminium)
- Panel brackets for the guardrail / pushpit (stainless)
clamps for 22–25 mm (0.87 in–0.98 in) tube, set of guardrail mountings€40–120 (≈$46–139) approx. - Set of corners / spoilers for semi-flex panels
ABS/aluminium profiles for bonding flexible panels to the deck€20–60 (≈$23–70) approx. - A2/A4 aluminium brackets / rails + bolts
frame for a rigid panel on the coachroof€30–90 (≈$35–105) approx.
Cable glands + PU sealant
- Seatec — deck gland with MC4 connector
watertight passage for the solar cable through the deck€14–18 (≈$16–21) - Sika — Sikaflex-291i (300 ml (10 fl oz))
marine PU compound for sealing glands and bases€8–13 (≈$9–15) - Sika — Sikaflex-295 UV
UV-resistant adhesive / sealant for bonding flexible panels€26–34 (≈$30–40) - PG/M cable gland (IP68)
gland for the junction box / controller€2–8 (≈$2–9) approx.
Cable ties + heat-shrink sleeves
- UV-resistant cable ties (black), set
securing looms outside, resistant to UV€5–12 (≈$6–14) approx. - Adhesive-lined heat-shrink sleeves, set
insulating and sealing the joints, various diameters€8–20 (≈$9–23) approx.
Battery monitor / shunt
- Victron — SmartShunt 500 A (Bluetooth)
battery monitor without a display, read in the app€110–130 (≈$128–151) - Victron — SmartShunt 1000 A (Bluetooth)
for larger banks and higher currents€150–180 (≈$174–209) - Victron — BMV-712 Smart (with display)
monitor with a screen and Bluetooth, 500 A shunt included€150–190 (≈$174–221)