Solar PV systems involve high-voltage DC and substantial fault currents. Improper installation can cause fire, injury, or death. Consult a licensed electrician and your local Authority Having Jurisdiction (AHJ) before any installation work, and verify every value against the current NEC edition and current product datasheets. Numbers and recommendations on this page are educational starting points, not a substitute for professional design and inspection.
Marine
Solar setup for a sailboat or power cruiser
A cruising boat at anchor typically pulls 1–2 kWh/day — refrigeration is the dominant load, with electronics, lighting, and water-making after that. The electrical itself isn't the hard part. The hard part is making every component survive salt-laden, vibration-heavy marine conditions for years.
Typical at-anchor load profile
- 12V refrigeration (compressor) — 50W avg, 24h → 1,200 Wh
- LED nav and cabin lighting — 30W, 5h → 150 Wh
- Plotter, AIS, anchor light — 20W, 14h → 280 Wh
- Autopilot (under sail) → 100–300 Wh
- Watermaker (1 hr/day, energy-recovery type) → 300 Wh
- Phone/tablet charging → 100 Wh
Total: ~2 kWh/day for cruising, ~3 kWh/day with watermaker. Liveaboards with air conditioning at the dock are a completely different problem.
Recommended build
Why these choices
12V over 24V on cruising sailboats stays compatible with the ABYC-standard 12V house bank that powers everything else (engine starting, nav, fridge, lights). Going 24V means a DC-DC step-down for everything, and marine-rated 24V-to-12V converters are expensive.
LFP over AGM — finally the consensus shifted around 2022. LFP offers 3× the cycle life, full DoD, weighs half as much, and the cost-per-kWh is now competitive. The only AGM advantage left is initial cost, and that's usually paid back in 18 months.
Flex panels on the bimini or dodger are the standard install for sailboats — they don't catch wind, mount with adhesive, and don't add windage. The downside is shorter lifespan (5–7 years vs 20+ for rigid). For rigid mounts, an arch over the cockpit is the right answer if your design allows it.
The marine gotchas
- Tinned copper wire only. Standard copper wire corrodes inside the insulation within a year in salt air. ABYC requires marine-grade tinned wire for everything — adds 30–50% to wire cost but it's non-negotiable for safety and reliability.
- IP67-rated connectors and enclosures. Anderson connectors, MC4s, and any control box exposed to spray needs better-than-residential ratings. Victron and Blue Sea make marine-appropriate equipment.
- Battery placement. LFP must stay above 32°F to accept charge. In northern winter lay-ups, either bring the batteries home or use self-heating LFP modules.
- Shore power integration. A galvanic isolator or isolation transformer on shore power is mandatory to prevent stray-current corrosion of underwater metals. Cheap to add, expensive not to.
- Inverter location. Inverters generate heat and need ventilation. Mounting in a damp lazarette will shorten life by 3–5×. Put them in a dry, vented locker.