Solar panels and narrowboats are a match made in heaven. Your boat has a long, flat roof that faces the sky all day long — it's basically a ready-made solar platform. Whether you're a weekend cruiser wanting to keep your batteries topped up or a liveaboard aiming for energy independence, solar is one of the best investments you can make on a narrowboat.
In this guide, we'll cover everything from choosing between rigid and flexible panels to sizing your system, picking the right charge controller, and getting the installation done properly.
Why Solar Works So Well on Narrowboats
Narrowboats are perfectly shaped for solar. A typical 60-foot boat has around 5-6 metres of usable roof space (accounting for the cratch, gas locker, and tiller area), giving you room for 800-1200 watts of panels. Even a 40-footer can fit 400-600 watts.
Solar reduces your dependence on the engine for charging batteries, which means:
- Less engine running time (saving diesel and reducing wear)
- Quieter days on the cut
- More freedom to moor away from shore power
- Lower running costs over time
In the UK, you'll generate most of your solar energy between March and October. In summer, a well-sized system can meet all your electrical needs. In winter, you'll still get useful power on clear days, but you'll rely more on the engine or a generator.
Rigid vs Flexible Solar Panels for Narrowboats
This is the first big decision. Both types work, but they have different strengths.
Rigid (Framed) Solar Panels
Traditional glass-fronted panels in aluminium frames, mounted on brackets above the roof.
Rigid Panel Pros
- Higher efficiency — typically 20-22% for monocrystalline panels
- Longer lifespan — 25+ years with minimal degradation
- Better airflow underneath keeps them cooler (heat reduces output)
- More watts per pound spent
- Proven technology with well-understood performance
Rigid Panel Cons
- Add height — typically 5-8cm above the roof, which matters for low bridges
- Heavier — around 10-12kg per panel
- Can be damaged by overhanging branches on tree-lined canals
- More complex mounting (brackets, rails, or frames needed)
Flexible Solar Panels
Thin, lightweight panels that bond directly to the roof surface.
Flexible Panel Pros
- Virtually no added height — bonded flat to the roof
- Very lightweight — around 2-3kg per panel
- Less likely to catch on branches or low bridges
- Cleaner look — less visible from the towpath
- Easier installation — glued directly to the roof
Flexible Panel Cons
- Lower efficiency — typically 15-18%
- Shorter lifespan — 5-10 years before significant degradation
- Run hotter because there's no air gap (reducing output by 10-15% on hot days)
- More expensive per watt
- Can be harder to replace — adhesive bonding is semi-permanent
Our Recommendation
For most narrowboaters, rigid panels on tilt brackets offer the best long-term value. However, if you frequently navigate canals with low bridges (anything under 6'6") or you want a sleeker look, flexible panels are a sound choice. Many boaters use a mix — rigid panels on the main roof and a flexible panel on the cratch cover or gas locker lid.
Sizing Your Narrowboat Solar System
The right system size depends on your electricity consumption. Here's how to work it out:
Step 1: Calculate Your Daily Power Use
List everything electrical on your boat and estimate daily usage:
- LED lighting: 20-40Wh/day
- Phone/tablet charging: 20-40Wh/day
- Laptop: 100-200Wh/day
- 12V fridge: 400-600Wh/day
- Water pump: 20-40Wh/day
- TV/entertainment: 100-200Wh/day
- Inverter standby losses: 50-100Wh/day
A typical liveaboard couple uses around 1,000-2,000Wh (1-2kWh) per day. Weekend users typically need less.
Step 2: Account for UK Solar Conditions
In the UK, you can expect an average of about 3-4 "peak sun hours" per day across the year (more in summer, less in winter). A 100W panel in 4 peak sun hours produces roughly 300-350Wh of usable energy (after losses from wiring, charge controller efficiency, and temperature).
Step 3: Size Your Array
Divide your daily consumption by the expected output per 100W of panels:
- Light user (800Wh/day): 300-400W of panels
- Average liveaboard (1,500Wh/day): 600-800W of panels
- Heavy user (2,500Wh/day): 1,000-1,200W+ of panels
It's always better to oversize slightly. Extra solar in summer costs you nothing, and it helps during cloudy periods.
Battery Bank Considerations
Your solar panels are only as good as your battery bank. The batteries store the energy for use when the sun isn't shining.
Battery Types
- Lead-acid (flooded) — cheapest upfront, but heavy, need topping up with water, and should only be discharged to 50%. Around £100-200 per 100Ah.
- AGM (absorbed glass mat) — maintenance-free lead-acid, slightly more expensive. Around £150-250 per 100Ah.
- Lithium (LiFePO4) — the gold standard. Lighter, can be discharged to 80-90%, last 3-5 times longer than lead-acid, charge faster. Around £500-800 per 100Ah, but falling in price.
Sizing Your Battery Bank
As a rule of thumb, your battery bank should hold at least 2-3 days' worth of energy consumption. For a 1,500Wh/day household:
- Lead-acid: 600Ah at 12V (using 50% depth of discharge)
- Lithium: 300Ah at 12V (using 80% depth of discharge)
Lithium batteries are increasingly popular on narrowboats despite the higher cost, because they're lighter, last longer, and work much better with solar charging.
Charge Controllers: MPPT vs PWM
The charge controller sits between your panels and your batteries, regulating the charge to prevent damage.
- PWM (Pulse Width Modulation) — simpler, cheaper (£20-50), but less efficient. Fine for small systems under 200W.
- MPPT (Maximum Power Point Tracking) — more sophisticated, extracts 15-30% more energy from your panels, especially in cloudy conditions. Costs £100-300. Essential for systems over 200W.
For most narrowboat solar installations, an MPPT controller is well worth the extra cost. Popular brands include Victron, Epever, and Renogy. The Victron SmartSolar range is particularly popular because it offers Bluetooth monitoring.
Installation Tips for Narrowboat Solar Panels
A few practical tips for getting your installation right:
- Cable sizing matters. Use cables thick enough to minimise voltage drop — 4mm² or 6mm² is typical for roof runs. Calculate based on the maximum current and cable length.
- Waterproof your roof penetrations. Where cables enter the boat, use proper cable glands and sealant. A leaky roof is no joke on a narrowboat.
- Fuse everything. Fit fuses or circuit breakers at the panels and at the battery bank. Solar panels can't be switched off — they produce power whenever there's light.
- Connect panels in series for MPPT controllers. This produces higher voltage, which means lower current and thinner cables. Your MPPT controller handles the voltage conversion.
- Consider a battery monitor. A shunt-based monitor (like the Victron BMV-712) tells you exactly how much energy is going in and out. It takes the guesswork out of managing your system.
- Leave access for cleaning. Dirty panels lose 10-20% output. If you can reach your panels from the towpath with a soft brush, cleaning is easy.
What Does a Narrowboat Solar Installation Cost?
Here's a realistic breakdown for a mid-range liveaboard system:
- 4 x 200W rigid panels: £400-600
- MPPT charge controller (e.g., Victron 100/30): £150-250
- Mounting brackets/frames: £100-200
- Cables, connectors, fuses, glands: £50-100
- Battery monitor: £100-200
Total DIY cost: £800-1,350
Professional installation typically adds £300-600 for labour. If you're also upgrading to lithium batteries, budget another £1,500-3,000 for a 200-400Ah bank.
The payback period depends on how much engine running you avoid — most boaters reckon solar pays for itself within 2-4 years through diesel savings alone, plus the comfort of silent charging.
Find Marine Electricians Near You
Not confident doing the installation yourself? A qualified marine electrician can design and install your solar system safely and efficiently. Use our directory to find boat electricians and maintenance specialists near your mooring.