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Solar installed - what next? Musings and advice

  • 03-04-2022 12:42pm
    Registered Users Posts: 4,951 ✭✭✭

    Have a 6.84kWh system in since the start of the year and am happy with its performance so far, but like most on here I'm looking ahead to see how to maximise usage and increase if possible.

    The install was 18 x 380w panels on the South roof of an outbuilding, if it was big enough I probably would have maxed it out with 3 more panels to 8kWh (on a 6kWh hybrid inverter) . East West aspects not big enough for additional panels. North side is same size as South so can fit another 18, but that'd be too much for the inverter.

    What I am thinking now is, using the solar calculator linked on here to spec it, 5 panels on the North roof would give the equivalet of those "missing" 3 panels on the south roof. It'd barely add anything worth talking about from Nov - Feb but would ensure March, September & October would, in theory, produce enough to cover full house consumption (though capturing/using it a different conversation). I'd never see payback on that though with, a guess at, install costing €1500 minimum. Not keen on tackling a diy job.

    Would it be worth it, bearing in mind the following? I'm leaning towards no.

    Longer term (5/6 years) we hope to build an extension to the main house which would have an east/west facing roof. So plan on installing another inverter then and filling those new roof aspects with (a guess of the size available) 4-5kWh. The main roof is also south facing but is old so currently isn't fit to install on, but could be factored in the future as it would be re-roofed with the extension. Though if limited to 2 strings, the east/west split would compliment the existing setup better.

    We also have another shed with a south facing roof that could fit 18-20 panels that could be utilised if needed for EVs in the future, though again using it as produced would need some planning. Are there any threads on here on having multiple inverters and utilising a 15-20kWh setup? Would I need a 3 phase connection for all that?

    Also keeping an eye on the recent thread on small wind turbines, more out of curosity, but would have room to mount one if it was ever worthwhile.

    Probably no point putting too much thought into now. The PV landscape could be different in 5+ years. Tech will improve and some elements (eg batteries) may be cheaper than now. Hell, FIT might have actually been brought in and manners put on suppliers over smart tarrifs and low (grid) usage charges.


  • Registered Users Posts: 2,529 ✭✭✭bullit_dodger

    Leaving aside the financials on the north roof for a sec (and the proposed extension), I don't think you have the capacity to do it (easily). You have 18 panels as you say on the south roof. Normally they are 40-45V each, meaning that (most) inverters max out with 12-13 panels per string. Since you have 18, I suspect that the supplier has set it up that both of your strings are used on the south aspect. So you would be looking at an additional inverter, or using optimizers, or reconfiguring the panel setup where you would have say 12 panels on the south aspect and 12 panels on the north one.

    That 12 and 12 isn't as crazy as it seems though. You'd be in about 9Kwp, and that would be about the max with a 6Kw inverters. Yes, your right they won't produce much from Nov - Feb (but they will produce something), however you still have a fairly substantial south aspect of 12, and overall I think you will increase the number of months where you are self-sufficient. In truth in the summer, we have more than we need, so it's improving the situation for Mar&Apr as well as Sept&Oct that you'd be looking at. A little depends on the slope of the roof, the more shallow the slope the better. I haven't' run the math, but gut feeling tells me that it's a runner. Limited work required too on the electrical side, it's just really a panel provisioning and roofing problem.

    As for the other musings, I don't know enough about installing 2nd inverters, etc, but I do suspect that you would need 3 phase, and then you would be able to export up to 11Kw (instead of the 6kw currently on 1 phase)

    Are you out "da country"?

  • Registered Users Posts: 4,951 ✭✭✭paulbok

    That's the blue sky thinking I came here for 😁. I think you are spot on re: 2 strings already in use. Never though of splitting them like that, will run the numbers and see. As you say it's more to optimise sufficency earlier and later in the year than a big surpluss in the summer.

    Aye, out in the sticks.


    Will check again tomorrow on the laptop, but a rough run through of 13 + 13 panels split N/S makes very little difference to current setup.

    Think I'd be better throwing that 1500 at another battery to lessen export and increase winter night time charging if I was to do anything at the moment.

    Post edited by paulbok on

  • Registered Users Posts: 2,529 ✭✭✭bullit_dodger

    Our of curiosity, I ran the numbers for you

    The 12-12 split is an "improvement" (loose term), but having seen the numbers, I'd probably pass myself. Generally adding North to the house is good, but in your case you'd be giving up a south panel to get 2 north panels and it's only marginal.

    If you could reconfigure the south array to get in more panels (landscape instead of portrait etc) that might be the way to go. Even 2-3 panels would be cost efficient.

  • Registered Users Posts: 6,780 ✭✭✭SouthWesterly

    Would putting in a 2nd inverter not bring you over the 6kw max output to the grid?

  • Registered Users Posts: 566 ✭✭✭idc

    There is at least one user on here with 2 x 5/6 kW inverters on single phase and use functionality of inverter to limit export. Probably something you'd want to confirm with esbn to be sure?

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  • Registered Users Posts: 6,215 ✭✭✭Ubbquittious

    People come into this forum and spend maybe a couple of k on a cheap enough solar install

    Few years later they upgrade to a 10+KW array with a rack full of pylontech batteries, two teslas outside the door, a couple of heatpumps, a high powered laser on the roof to beam surplus power to their granny's cottage who lives up the mountain (u have to make sure to align this properly to prevent the thatched roof catching fire) and their wallet about 200k lighter.

  • Registered Users Posts: 2,335 ✭✭✭SD_DRACULA

    Ugh Teslas 🤮

    I'll take the i4 over any Tesla any day (yes I drove all of them)

  • Registered Users Posts: 2,529 ✭✭✭bullit_dodger

    Just to be clear (and jokes aside about the laser to grannys house - LOL), you see the adoption of greener technologies as a bad thing? Not sure I've ever heard anyone arguing that spending hard earned wonga on renewable technologies and trying to do right by the environment.... is not to be encouraged.

    For sure - there are limits, and after a point you very much get into the law of diminishing returns, but it's their wonga, no? How they spend it is up to them, and if they feel better adopting some green tech, that's got to be good no?

  • Registered Users Posts: 7,407 ✭✭✭MrMusician18

    I think maybe his point is that people easily lose the run of themselves as sell themselves the idea that they are making long term savings on these large investments in technology.

    If I were to recommend anything when it comes to this tech - is that you need to remain level headed. Building a solar Moneypoint out the back might be the dream, but you'll never get a return or indeed break even. Not unless there is a radical policy shift - and that's a gamble.

  • Registered Users Posts: 2,529 ✭✭✭bullit_dodger

    Ohh very true MrMusician - and something that I mentioned myself that, after a point the "law of diminishing returns" sets in .... but no my argument was more that it's their cash, up to them how they want to spend it. If they want to spend it on "shiny magic beans" (LOL) ..... then that would be up to them.

    I think sometimes looking at these things as purely as "How long will it take me to payback?" or "How much money will it save?" isn't always the right way. Ohh for sure, you don't want to be taking out bank loans to save a few hundred a year, but there are other reasons to adopt energy saving tech. Financial impetus helps people "get in behind" this stuff, but even knowing that whoever gets this house after me will inherit an abode that hopefully has a decent energy footprint.....and that's got "value" to me.

    But yeah....each to their own I guess.

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  • Registered Users Posts: 6,215 ✭✭✭Ubbquittious

    I don't see it as a bad thing unless they spend too much and are facing into multiple decades of praying that stuff doesn't pack up in order to break even. By the time someone inherits the place anything they buy now will be old hat and obsolete anyway. Cars are generally also a terrible investment.

    I can see how fellas would be inclined to fall into the trap of buying stuff in order to use up the excess power they're now generating. This is mainly down to the nonexistent feed-in tariff we are getting. The right job for fellas looking to invest would be a proper community run solar farm. It is unfortunate but unless we group together the elite in the energy sector & their government buddies will keep taking free power off our hands

    The way things are headed now with power companies increasing their prices & standing charges every few months the off grid lifestyle is looking more tempting, with the availability of cheaper batteries you wouldn't even need gas for cooking anymore.

  • Registered Users Posts: 2,529 ✭✭✭bullit_dodger

    I did think awhile back on a similar proposition. Some company would setup a field somewhere and you'd "buy your panels" and what not from that supplier. A little bit like "solar as a service", but not with panels on your roof, but somewhere else. You effectively pay them for the panels, and get the excesses when it's sunny.. and crap when it's a dull day.

    We're not there yet. Could happen one day, but for now we're limited to panels on our roof. One good thing that we have, is that in the last 10 years, the prices have dropped like a stone! It's a mature sector now and (cowboys aside) most suppliers are reputable and give decent value for money that you will see payback in a decade, mostly. After that your "quids in", but more importantly from the day it's commissioned your helping reduce your footprint. .

  • Registered Users Posts: 4,951 ✭✭✭paulbok

    One thing is for sure, the recent ~25% unit rate increases by most suppliers has knocked anything from 1-2 years off the payback. Estimate 16 months less for my system.

  • Moderators, Home & Garden Moderators Posts: 6,095 Mod ✭✭✭✭graememk

    My next step, Mainly for spring/autumn. That i'm looking into fairly seriously is a hot water "battery" or buffer tank, connected directly into the heating of the house.

    Goal is to burn less stuff. Looking into a 500L buffer tank with immersions. These days the house still needs some heat in the evening. So if I can charge that up and then the heat will come from that first before either the boiler fires up or light the fire.

  • Registered Users Posts: 189 ✭✭connesha

    You wouldn't consider a Storage Heater for the same purpose? Could be much easier to setup, and run off the Eddi its set-and-forget. Putting near 10kwh in each day these days, and is taking the chill out bedrooms these nights.

  • Moderators, Home & Garden Moderators Posts: 6,095 Mod ✭✭✭✭graememk

    Yeah.. but they are fugly 😂/nowhere to put it really, whereas the tank will go where it's needed.

    I also think I'll be able to charge it from the stove in the winter...

    I do have access to one that's not being used currently though, the thought did cross my mind.