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The Ultimate Guide To Narrowboat Solar Power – Part 3

You can read part 2 of this 3 part narrowboat solar power article here.


My approach is to offer a complete functioning solar system mixing the best available panels and controllers with in house developed mounting and cabling systems Customers will often ask us to deviate from what we do perhaps using other panels, controllers or mounting systems however we don’t deviate from what we know works well as we have a very well tried and tested system now with over 2000 boats out there. We are in 2021 on our 4th generation of systems. The basic proven qualities of the systems however have pretty much remained unchanged. 

Tilting Bracket System 

We use an in house designed triangular shaped laser cut bracket system that enables the panels to tilt up to 40 degrees to the left and right and also a limited tilt for and aft. The top of the bracket is shaped so that the brackets can “lock” at the top or panels may be slid down a slot on the bracket to sit flat on the roof. 


Where to position panels on the roof. 

The tilting bracket system means we do not have to worry too much about roof furniture and particularly roof vents (mushrooms). Lots of factors affect where the panels can go but the absolute ideal that we strive for is to have them in a row, down the centre line of the boat. Most of the time this can be achieved but the following factors can affect where they can go.

Length of the boat 

It goes without saying really that shorter boats have less room available for panels. 2

Roof hatches 

Some boats have triangular raised pigeon boxes, some have glass “Houdini” hatches or lift up lids above side doors where side doors are designed as an access point.

Pole and plank racks 

These racks designed to hold a boarding plank and a pole plus usually a boat hook of some kind can be a real nuisance. Panels can, of course, be mounted above them as the tilting brackets allow this BUT if we mount them over the rack then it tends to limit the tilt in that direction. I  always point this out on the install and debate the options with the customer. Sometimes we can offset the panels one way but still close to the centre, sometimes if we are lucky the brackets are far enough apart so that the panel will tilt in-between them. Sometimes though especially on a bigger multi-panel system where there is plenty of power “headroom” we just accept the loss of tilt one way on one panel. 

A look at different Installations – 2 Panel our entry-level system 

Two solar panel entry level system

Three Panel System – The most popular good “all-round” system 

Three solar panel system

A three-panel 645W system. Once again installed in the absolute optimum fashion. I.e. down the centreline of the boat. This is our most popular system. Offering 645W of power it performs well generating 40A of charge on a good summer’s day, but a high average even on duller days. It will support a 240V fridge most of the time but as I bang on all the time – a 12V fridge is always a better option. 

Four Solar Panel System


6 Panel System 1.2KW 

Six panel solar system

This is really the largest system that can reasonably be accommodated on a narrowboat. It usually requires a length of at least 60ft and with a very clear roof (probably only mushroom vents). This comes with a 60A controller and easily achieves this output on average to good days. For those boaters insistent on relying on 240V fridge, 240V freezer and other power-hungry appliances, and assuming they have a long enough boat and a fairly deep pocket,  this is the one! 

Other Considerations 

I have mentioned that pole and plan racks can be an issue, as can hatches other issues can cause grief. However, there are other things to think about… Offset mushrooms can be an issue. Some boats, especially older ones can have mushroom vents dotted around on the roof rather than in a straight line down the middle. This can again mean panels will have a  limited tilt one way unless we offset them to avoid the offset mushroom. 


Chimneys are another issue as they can shade a panel, recommendation here is to have a  chimney cap that will allow it to be removed in the summer.

The centre line 

The centre line is another big consideration. Most boats have a centre eye to which the centre rope attaches. I always recommend two centre ropes, one for each side. I would even recommend this were solar panels not installed as you can have a line running down each side back to the steering position ready to grab when you step off without having to flick it across the cabin roof. Once solar panels are in place this of course becomes more critical.  The second problem with the centre line is it is normally used in wide locks to secure the boat. In wide locks, the boat can move forwards and backwards quickly meaning the centre line can be at quite an angle. This means we have to leave a sensible gap between the centre eye and panels. On most boats of the standard 58 to 60ft length I generally find it’s very possible to fit two panels at the back before the centre line, then a gap of 18 inches or so before the centre eye then another gap then two more panels forward of the centre line.  

Some boats have “pipe rails” these are raised handrails made from a pipe. Often these are used to tie the centre line to which is great as any issues with “snagging” the panel go away.  Where there are pipe rails and a centre eye I tend to recommend the centre lines are fed under the pipe rail while cruising which also stops the lines from “interfering” with the panels.

Installations where we can’t use the optimum positioning: – 

2 Panels side by side 

Two solar panels side by side

Panels Athwart the Boat 

Two solar panels across the boat

Wide Beam 

Wide beam boats give far more scope for panel positioning. Again there is an ideal and this is to have panels located in either a single linear row or two linear rows. Here are some examples. 

Wide Beam Four Solar Panels

On this 6-panel wide beam system, the panels are installed in two sets of three ensuring there is a decent enough gap between the two arrays so that they may be tilted without causing shading issues.  

Wide Beam Six Solar Panels

A note about our cabling systems 

This is a good photo to see our bespoke cabling system. We use multi-core armoured cabling. We run a heavy-duty multi-core to the first array and then a lighter-duty armoured multi-core to the next array. These cables are pre-made on the bench to a high standard and are bombproof. The problem with regular solar spec cabling is it is designed to be used on a building roof where there is no chance it will be walked on or have bags of coal dropped on it. The other disadvantage of single core solar cable is of course you end up with many individual runs which on a boat where you see the roof up close every day would look quite messy.

Four solar panels on a Euro Cruiser

A 4-panel system on a wide beam Euro-style cruiser positioned around the huge ceiling skylight.

Six solar panels on a wide beam

Another 6-panel system on a wide beam. Notice the break between the first pair of panels and the other 4 to allow for the centre line to swing without any issues. Particularly important while in a wide lock controlling the movement of the boat from above. Note the customer was advised as I stated earlier to purchase a second centre rope so one could be drawn to the back of each side. 

Wide Beam Observations 

We have tended to fit larger systems on wide beams, not just because there is more space to play with but also wide beam boats tend to be built and configured to live in a marina plugged in, so they have big 240V fridges and freezers and 60 inch TVs etc. So the power requirements are much higher. Strangely (I think in part because they are not expected by the boat builder to be cruised much) they often have quite small battery banks so often the solar project also involves adding extra batteries. Will come back to batteries later.

8 solar panels on a hotel boat

8 Panel System on a wide beam hotel boat. 

This is approaching the realistic maximum that we go to. With our latest generation panels, this would be 1,720W of output. We would run this in two separate 860W arrays with dual  40A controllers. This was a wide beam hotel boat with very high power requirements in the form of multiple refrigeration devices plus microwave ovens etc. Note the shading in the photo and you can appreciate why you would not want panels side by side on a narrowboat.

Examples of compromise systems  

Here are a couple of examples of systems where my ideal of having all panels in a row down the centreline could not b achieved and show possible solutions to get out of these problems. 

Compromise solar system

Here is a 6-panel system on a narrowboat. The customer had already had the centre line points moved to the side of the boat meaning we didn’t have to worry about a gap there but the pole and plank rack presented an issue for tilting the first two panels. The solution on this occasion to maximise the flexibility of the whole system was to offset the first two panels. We could indeed have kept them in the centre, but the first two panels would then have had a limited tilt to the right…These are the sort of issues we debate on the day of the install, often until we put the panels u on the roof it is hard to see the issues!

Wide beam compromise solar system

On this 4 panel system on a wide beam, we had a number of issues, pole and plank rack at the back, chimney and a requirement for a future storage box and satellite dome further forward. We also had a technical issue of hitting the limit on cabling length – not a problem additional cables could have been added but would have not been pleasing to the eye.  Hence the solution above of two in a row in the centre – the best option and two forward side by side.  

These system photos are a small selection of the 2000 odd systems we have installed. But hopefully, go to show there is always a way of making it work in such a way that it is fully functional and pleasing to the eye. We always start with an idea of where they should go then work from there.

Fitting Methods 

Brackets are made of aluminium to match the frame of the solar panels.  

Solar panel bracket

Solar panel bracket

Mounting Panels to Bracket 

The panels are drilled and threaded on their narrow ends. We then use a button head A4 marine grade stainless machine screw to attach the panel to the bracket. Now both brackets are fitted the panels are set to lodge in one of the notches in the top of the panel. When in a single line we take care to ensure all panels are orientated on the same side of the bracket for neatness  AND most importantly that all panels are perfectly lined up. As the panels have grid patens on top where the solar cells are located any miss alignment is very off-putting to the eye. The button head machine screw and A4 marine stainless washer used are shown in the bottom photo lower half. The screw can be tightened or loosened with an Allan key (provided as part of the installation) 

Fitting Brackets to the roof 

Here we drill and then cut a thread in the roof (tap). We then screw in a type of stud called a grub screw. This is bedded in with a compound called marine flex a high-quality underwater grade sealant.  

Once all 4 grub screws are in place we drop the assembled panel and bracket straight onto the studs. Then a washer is added and a flange nut for neatness, both A4 marine stainless. Before tightening down there is enough play in the bracket holes to allow for very fine alignment adjustment. 


Solar panel controllers

We have adopted the Tracer (now known as Epever) range of controllers for all our systems.  These are very highly rated MPPT controllers within the industry. At one time we used to offer them with a secondary remote display but the new generation Xtra units we are now using have a much more comprehensive built-in display and also have the option for those who love modern tech, of being managed from an app on your phone via Bluetooth. This app and the display on the controller allow you to see what you are putting into your batteries.  

I also recommend consideration of a full battery monitoring system. The solar controller tells you what you have going in from the solar, but not what is going in from the engine nor does the solar system have any knowledge of what you are drawing in the boat. A full battery monitor would give all of this info. 

Solar panel battery monitor

There are many makes of battery management system. This one the NASA BM2 is a nice one as it gives all the info on one large screen. It shows battery voltage, current in and out via all charging methods and a percentage state of charge. While not directly connected with solar it is a great additional tool for off-grid living.

Batteries and Battery Banks 

The intention here is not to go into lots of technical detail about batteries but to give some general advice and comment on the technologies at a practical level.  

Batteries are ultimately the key to a good power setup but in reality, have a very limited amount of stored power as you may only access around the top 1V of the batteries capacity as the remainder is required to keep the battery in good condition. 

Traditional analogue voltmeters show the entire voltage range but this is not very useful when we are only interested in the range 12.6 to 11.6  

Battery voltage chart

This table shows what we call your “usable” window of power.  

Batteries will be between 12.6 and 14.4 when they are charging off of solar, alternator or charge but once charged will sit at 12.6. Roughly each 0.1 of a volt is 10% of your battery capacity. I generally don’t recommend regularly going below 11.6. So 12.6 to 11.6 in 0.1v increments is your 10% chunks of power. 

Your solar controller gives you a DIGITAL readout of battery voltage so using this simple voltage guide you can keep a close on where your batteries are in this tiny voltage range.  Alternatively, a true battery-monitoring tool as described in the pages above will give you a  very accurate percentage state of charge as it records all power that goes IN and OUT.  However, as I say a basic understanding of the voltages gives you a very good idea. I am amazed how many boats I install solar on that until that point have no way of monitoring voltage.  

Another low-cost alternative is a battery condition meter. This doesn’t have volts on it and is set to measure the 11V to 14Vv range with green, yellow and red sections. When charging the needle heads to the charge area and then works its way through the yellow to the red discharge area once you hit below 11.3v. These are also available in LED form with red amber and green LEDs. At the end of the day though a digital readout and an understanding of voltage ranges is all that is needed.

Battery Banks 

To give plenty of stored power batteries are banked together. The common battery seen out there is the 110AH lead acid leisure battery. Generally, 4 of these is the minimum needed for successful live-aboard use. Alternatively, a minimum of 3 x 130ah slightly larger lead-acid is also the minimum sensible battery bank. Newer 130ah batteries these days are the same physical size as 110ah batteries so a 3 battery 110ah can easily become a 3 x  130ah for example. These two specs of batteries are the most common I see out there. It is very important BEFORE thinking about solar that the batteries are known to be in good condition and the bank of sufficient size. As batteries age, they do not hold onto a charge as well as they did, eventually not holding a charge at all. The give away here is after doing a  long run the batteries only keep things running for a couple of hours. This problem does not go away by fitting solar. They will merrily charge all day off the solar but do not hold it through the evening and night. This is a sure sign that batteries need replacing! 

AMP HOURS or AH is a measure of how much they store. Going back to my recommendations for trimming your power down you could see that a unit on the boat such as a 240V fridge could draw 10amps let’s say. This would equate to 24 x 10 or 240ah per day… So the bigger the bank the better right? Not exactly as too big a bank will take too long to charge hence optimum bank size. Remember once you have solar the batteries  ONLY have to get you through the night time period. Short in the summer and LONG in the winter. The 4 x 110 or 3, 4 x 130 is a good optimum size to achieve this. It is generally considered the max sensible bank is 5 batteries. 

Gel or AGM batteries 

These use a non-liquid electrolyte and were originally designed for applications where the battery might get tipped over – planes, yachts etc. They are available in various AH sizes running up to large capacity of 300+ah units. Gel batteries cost more but have a longer service live – I’ve seen them up to 10 years old and still performing well. Capacity and power delivery wise though they are the same as the lead-acid type. 


Lithium batteries are the latest thing – using the same technology as in your mobile and all other tech devices they offer the ability to be drained right down while delivering steady voltage and current so in theory, a smaller bank will deliver power for longer than a  traditional battery. This is the same technology used in electric cars. At the moment, however, there are no real standards for lithium batteries and they require very carefully managed charge regimes so connecting an alternator directly to a lithium battery without the right power management in place is not good. Additionally, right now they are very very expensive. I think I would advise waiting a bit before considering lithium as your domestic bank though I should point out our controllers do fully support lithium charging it is just not quite mature enough yet or cost-effective to be a good option in my opinion.

Living with Solar 

The system is pretty much maintenance-free. However, there are some useful tips:- 

  1. It is worth keeping the panels clean (quick wash over with something like washing up liquid and water, rinse off with canal water).  
  2. Tilt into the sun. This will depend on lots of factors. If you have motored all day and are only staying overnight then off again in the morning it probably doesn’t matter too much. But if you are staying somewhere for a few days then it pays to make use of the tilt if the sun position is good (you will learn the places where solar can be best optimised). Given you are there a few days it’s worth tilting them into the evening sun than before bed tilting them in the direction of the rising sun. Works great in the summer when the low sun comes up at 4 and hits the panels. Often  batteries are fully charged by the time you get up to make the first cup of tea (or  coffee!) 
  3. Pick your mooring spot. Again if staying overnight only it probably doesn’t matter,  but if staying for a few days make sure there are no trees to shade the panels and avoid cuttings or buildings close to the canal. Often it pays to check “round the next bend” for a better option if you know you will be sitting there for a few days. 
  4. Monitor the system. During an average to good day, during the daylight, your controller should show a charge voltage of between 12.6 and 14.4 volts. Then once it goes dark rapidly drop to 12.6 as stated in the section above. It is then worth checking periodically where that voltage has got to. This gives you a clue as to how quickly you are depleting the bank. On a dull winter day, there may be minimal charge coming off the solar array and you may notice voltage already at say 12.1 at lunchtime. This would quickly tell you there is not enough charge coming in and you may have to supplement it with engine running. If your solar system, battery bank and power draw have been set up correctly though and IT DOES NEED ALL THREE OF  THOSE THINGS, then you should only rarely need to run your engine and only on the very worst of winter days. 

Example System Pricing – Jan 2021 

All prices include installation wherever your boat is. 

2-panel 430W system £1,050 

3-panel 645W system £1,395 

4-panel 860W system £1,695 


Understanding VOLTS, AMPS and WATTS in a 12V System 

Voltage diagram

The easiest way to understand the relationship between Volts, Amps and Watts is to treat them as if they were water… 

? VOLTS – This is your stored “tank” of energy. The main problem with a 12V  battery “tank” though is that the water outlet is very high up in the tank as can be seen in the diagram. Imagine a pipe above the tank flowing into it – this would be your alternator, charger or solar 

? AMPS is the flow of “current” or water from (or to in the case of charging. 

? WATTS is the actual thing using the power (or generating it) suh as a fridge,  pump etc