Solar Panel Size Calculator for Boats and Marine Use

Boat / Marine Solar System Guide

Marine solar installations face challenges not present in land-based systems: salt air corrosion, space constraints, moving targets for shade calculations, and the critical importance of wire and connection quality in a wet environment. Marine-grade tinned copper wire is mandatory — standard copper wire corrodes rapidly in salt-air environments, causing resistance increases and connection failures. All connections should be made with waterproof heat-shrink butt connectors or crimp terminals, not wire nuts.

Sailboat arch mounts are the ideal location for rigid solar panels because the stern arch is unshaded in most pointing angles and provides a robust mounting platform. A 300–400W array on a sailboat arch charges a 200Ah LiFePO4 bank in 5–6 hours of direct sun. For boats that spend time in marinas connected to shore power, an inverter-charger like the Victron MultiPlus handles both shore power charging and solar charging automatically, switching between sources as available.

Powerboats have less solar-friendly toplines than sailboats — flat surfaces get shaded by T-tops, towers, and radar masts. A T-top-mounted 200W panel combined with bimini-mounted flexible panels is a common powerboat configuration. For a boat used primarily at anchor or mooring rather than underway, solar is the cleanest solution. A 300W array and 100Ah LiFePO4 maintains a coastal cruiser indefinitely through an anchoring season.