You are my sunshine…

We’ve just had a solar/battery system installed, and because I’ve spent a lot of time planning and thinking about this over the last year and a half, and because it has some slightly unusual aspects, I decided to create a video about it.

This starts off as a pretty basic introduction of solar power, and ends up going into some detail about why mine is arranged the way it is. This means that it’s longish… but I hope it might be of interest to anyone considering installing, or expanding, a similar system.

(Direct link)

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Great video! I’m slightly puzzled as to whether the batteries are charged using inverter power or whether they take the DC direct from the solar units. Also would be interested in having some idea of the costs involved and the ROI

Hi Geoff –

Yes, I realise I should have gone into a bit more detail about that… but it might have made the video a bit long!

Some systems have a separate inverter/charger for the batteries, but with the Sunsynk, it’s all in the one ‘hybrid’ unit. The DC world, both batteries and solar, are on one side, and the batteries can be charged directly from the solar. And the AC world is on the other.

So the unit is bidirectional: at any one time it is either operating as an inverter, if the net flow is from DC to AC, or as a rectifier, if the net flow is from AC to DC, when you’re charging the batteries from the grid (or from other AC sources such as a generator).


An excellent overview that I have bookmarked as a future reference. Thank you for taking the time and trouble to make it. I am very envious of your admirably comprehensive system. Beautifully thought through.

Have you spotted the slipped slate at 2mins 31secs?

A very good explanation. I’m particularly interested in how you’re using the immersion heater and car as dump loads for your excess solar during the day. Many questions: do you monitor water temperature to control it? and what would happen in the situation where everything is fully charged/heated; are all loads disconnected and it effectively runs open circuit?

I’d be keen to see more on your experiences in the future, particularly on how you automate it.

    Hi Tim –

    I don’t monitor the water temperature directly – there is an add-on board for the Eddi which can do that, but it’s remarkably hard on my tank to find a place to install the thermometer! However, the immersion heater has a thermostat built in, so when it gets to a suitable temperature, the Eddi finds out it can’t supply power any more.

    At present, if all the batteries are charged and the water hot, I export power to the grid, for which I currently don’t get paid, but hope to get a few pence in future once the last few relevant forms have been filled in!

wotalotakit. It’s disappointing that the current energy market means that the sane thing for an individual to do with electricity that cannot be immediately used is to dump it as heat into hot water. I do think that, with sufficient changes to the grid, it would make sense for consumers to form groups of power generators.

fwiw, I’ve found that wireless controls work, mostly ok for solar and monitoring electricity consumption (I use a ZWave device with a RPi.) For long ethernet runs, I think it’s worthwhile checking power over ethernet to reduce the clutter a bit. It’s definitely worth getting the remote monitoring and logging set up so that you can work out what’s going on. Although I think it supports my hypothesis that home automation requires an in-house IT dept to keep it running 😉

Hi Quentin, thank you, it is a great description. I plan to install solar panels this year, I will get one company to design and install the whole system so it is very useful to know what to ask for and specify.

I am sure everyone is interested in the payback period, but I guess you need data from all 4 seasons to estimate it.

Please keep posting !

    Hi Antony –

    Yes, the payback period is hard to guess; it’ll depend on future energy prices, and on how efficiently I manage both to capture sunshine and to use cheap-rate electricity, and so on… most of which only time will allow me to tell!
    It was, of course, also more expensive than some comparable systems because of using in-roof panels etc.
    I’m assuming it’ll probably be around 15 years, but it’s also quite likely we will have moved by then, so the other question is what difference it might make to the value of the house!


Hello Quentin,

I would be fascinated to know if this actually works, can try it without disturbing your neighbours ? !


Hi Quentin, this might seem a stupid question but I’m going to ask it anyway. Many friends are disinclined towards electric cars because of the relatively limited range and the length of time it takes to recharge versus the 5-10 minutes to fill with petrol. They all are afraid that they’ll run out of power some distance from home. My postman worries that he won’t complete his round on a cold day because the heater sucks so much power from his electric van’s battery.
Assuming your Sunsynk batteries were in a more accessible location, can you take one from the rack and stick it in the boot of your Tesla to extend the range of the car?

    Well, you could almost construct such a system, but the car manufacturers don’t currently allow you to connect anything to the charging circuitry while you’re driving. You could have a battery and an inverter in the boot, but you’d have to stop and plug it in to the external socket, and charge rather slowly!

    As someone who’s been driving only electric cars for over seven years, I can say that I’ve never run out of power. In fact, in my lifetime I’ve run out of petrol more often then electricity!
    One key thing people forget is that, in extremis, almost every single 13A socket in Europe can be used to charge your car, albeit slowly… but you could get enough to get to the next fast charger that way!

    The other thing is that, though a modern car and charger might take you 20-30 minutes to fill up instead of 5-10 when on a long journey for a holiday, you can be in the car watching a movie or in the cafe enjoying a coffee at the time; you don’t have to stand by the car! And think of how many times you don’t have to go and stand in a smelly petrol station for the whole of the rest of the year… it actually takes you less time over all. And so on…

    My postman does have an electric van, BTW…

Hi Quentin,

Havw you installled separate consummer units for wach output from the Inverter? Also it looks like you have 3 outputs but I thought there were only 2? A curcuit diagram of the installation would be very interesting if you have one you could share.

Best Wishes


Hello Quentin,

Now that your solar system has operated through all 4 seasons, it would be really interesting to hear about the total power generation and other observations of your system and how it compares with your original expectations.

Apologies if you have already posted on your site and I missed it.

Best wishes, Antony

Now that your solar system has operated through all 4 seasons, it would be really interesting to hear about the total power generation and other observations of your system and how it compares with your original expectations.

Apologies if you have already posted on your site and I missed it.

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