Solar panels and inverter for narrowboat

Hi Andy,

Having had a good look around your website, I'm hoping you could give me a bit of advice about renewable energy options, as a novice narrowboat owner who knows very little about boat electrics – so please forgive my ignorance!

Firstly, generating electricity – battery-wise, we've got 3 new domestic batteries connected to an Adverc system, and I'd like to be able to charge these without having to use a separate generator. I was therefore thinking of investing in a sizeable solar array, maybe a single 130w Kyocera panel, or a couple of 65w panels, plus a controller. I'd just like a very rough idea of whether or not this would provide a reasonable amount of power for us, living aboard, without having to run the engine all the time, or whether we should be thinking of investing in a larger array? I know that this is a difficult question to answer without knowing the specifics, but basically, we're not planning to use the fridge over the winter (we've been told that they use a lot of power), so it'll basically be running the lights, water pumps and TV / stereo in the evenings and at weekends over the winter, and then the fridge as well in the spring / summer (when I presume we'll be getting more power, as the light levels increase). We're likely to be cruising most weekends, so we'll be generating power from the engine on a fairly regular basis. Do you reckon the combination of solar panels and sporadic engine-use is likely to be sufficient, providing we're careful with our power usage, or is it inevitable that we'll end up needing a generator of some sort, as some people seem to think?

Secondly, using appliances – we've got a 650w inverter on the boat at the moment, but I'm thinking of upgrading to a 1000w Silverline model. There are 240v sockets down one side of the boat and an external hook-up socket for shore power. It's been suggested that we should just use this system for our normal appliances, rather than muck about with wiring things into the 12v system. We're not going to have a shore hook-up, so it seems that we're going to need to have an inverter more or less permanently connected to the battery bank, with a lead running outside to plug into the external socket, to power up the internal 240v sockets. I'd just like your opinion of whether or not this sounds like a sensible and safe way of doing things – specifically, how efficient are inverters? Are we likely to be losing a lot of power by running our appliances like this? Also, is it safe and efficient to have an inverter permanently connected to the batteries like this – do they still draw power when nothing is connected to them, and do they get hot after prolonged usage? I'm guessing that the unit is designed to just cut-out if overloaded with too many appliances (although we're not planning to run anything more heavy-duty than e.g. a TV and DVD player off it).

Lastly, I'm assuming that all of this stuff is pretty easy to install and connect up to the batteries? At the moment, I'm at the bottom of a pretty steep learning-curve when it comes to most things related to boat maintenance, but I think I can cope with a bit of very basic electrical DIY.

Any advice would be very much appreciated!

Many thanks, Jon

Hi Jon,

It's certainly possible to run narrowboat electrics all through the year just from solar panels - I manage it on my own boat! That said, even with a biggish array (about 200W) I do have to be pretty careful in winter to keep usage down.

I would think a 130W panel would be a good choice based on what you expect to run. That would certainly have no problem at all in keeping up with lights, water pump and stereo use (though having energy efficient fluorescent or LED lights is well worthwhile to make sure of that). Fridges and TV do take a lot more power - but if you are happy to turn your fridge off in the winter, and are also able to get a bit of charging from the engine at weekends, I would think a 130W panel would be ample 90 or 95% of the time. Just occasionally if you are using systems heavily, and have a few overcast days, you might have to turn on the engine to charge - but I would think that would be rare.

Inverters are about 90-95% efficient, and draw a pretty low current when nothing is connected, so yes, they can be a sensible way of running appliances. It's no problem to leave them on all the time, and they do have thermal cut-outs if you do ask too much of them. I run a 240V fridge in summer for example - it was about 1/3 the cost of the equivalent 12V version, it means I can get away with thinner wiring, and there is little difference in the power it draws.

Wiring of a solar panel is extremely simple - two wires from the solar panel to the regulator, and two from the regulator to the battery. An easy DIY job. Wiring an inverter is equally easy - two big fat wires from the inverter to the battery. Having said that, they are 240V appliances, so if you are then wiring the inverter into a distribution system, you might want to have someone qualified to make sure it's all safe. Also, running a cable outside from the inverter, to then bring it in again through your shore power inlet is perhaps not the neatest way of doing things - it shouldn't be hard to simply rewire your distribution system direct to your inverter.

hope that helps, Andy