What Size Solar Panel Do You Need for a Small Boat?
Solar panels are becoming increasingly popular on small boats — and for good reason. They’re silent, low-maintenance, and perfect for keeping batteries topped up when your boat is sitting on a mooring, trailer, or pontoon.
But one of the most common questions is:
“What size solar panel do I actually need for my boat?”
The answer depends on how you use your boat and what you want to power. Let’s break it down in plain English.
Step 1: What Are You Powering?
Start by listing the electrical items on your boat. Most small boats fall into one of these categories:
Basic setup (very common)
- Navigation lights
- Anchor light
- Fish finder / depth sounder
- Phone charging
Moderate setup
- VHF radio
- GPS / chartplotter
- Bilge pump (automatic)
- Deck or cabin LED lights
Heavier setup (less common on small boats)
- Cool box / small fridge
- Multiple screens
- Stereo system
Step 2: Typical Power Use on a Small Boat
Here’s a rough idea of daily power consumption for a small fishing or day boat:
| Equipment | Approx Daily Use |
|---|---|
| Fish finder | 5–15Ah |
| VHF radio | 3–6Ah |
| LED lights | 2–5Ah |
| Phone charging | 1–2Ah |
| Bilge pump (standby) | 1–3Ah |
Typical total:
➡️ 15–30Ah per day
Step 3: Choosing the Right Solar Panel Size
Solar panels don’t produce their full rated power all day. In the UK, you should assume 4–5 hours of decent sunlight in summer, less in winter.
Recommended panel sizes for small boats
🔹 20–30W panel
Best for:
- Battery maintenance only
- Boats sitting unused for weeks
- Keeping a battery from going flat
✔ Good for moored or trailered boats
❌ Not enough for regular use
🔹 50–60W panel (most popular choice)
Best for:
- Small fishing boats
- Day boats
- Light electronics use
✔ Keeps up with fish finders, lights, and VHF
✔ Ideal for 12V systems
✔ Affordable and compact
👉 This is the sweet spot for most small boats
🔹 80–100W panel
Best for:
- Heavier electrical use
- Longer trips
- Boats with multiple electronics or a fridge
✔ Can actually recharge batteries, not just maintain them
✔ Good for weekend use without shore power
Step 4: Battery Size Matters Too
Your solar panel should match your battery setup.
Common small boat batteries:
- Leisure battery: 85–110Ah
- Dual battery setup: 2 × 90Ah
As a rough guide:
- 50W panel → maintains 1 leisure battery
- 100W panel → supports 1–2 batteries with moderate use
Step 5: Do You Need a Solar Charge Controller?
Yes — always.
A charge controller:
- Prevents overcharging
- Protects your battery
- Improves efficiency
Which type?
- PWM controller: fine for panels up to ~100W
- MPPT controller: better performance, especially in poor light
For most small boats, a simple PWM controller is perfectly adequate.
Step 6: Mounting Considerations on Small Boats
Space is often limited, so consider:
- Cabin roof
- Canopy or sliding roof
- Rail mounts
- Portable folding panels (great for small open boats)
Make sure the panel:
- Isn’t shaded by rods, rails, or antennas
- Is securely fixed (marine environment = vibration!)
Quick Recommendations
✔ Occasional use / battery maintenance
Panel: 20–30W
✔ Small fishing boat / day boat
Panel: 50–60W
✔ Heavier use / longer trips
Panel: 80–100W
Final Thoughts
For most small boats in the UK, a 50–60W solar panel is the best all-round choice. It’s powerful enough to keep your battery healthy, compact enough to fit on a small boat, and affordable.
Solar won’t replace an engine alternator — but it will mean:
- No flat batteries
- Less engine running
- More time fishing and boating
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