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Big south facing roof, what can I expect?

  • 30-07-2022 9:21pm
    Registered Users Posts: 125 ✭✭

    Howdy. I’ve been trawling through the threads here and getting lots of great info, but hoping to get some real world advice/figures.

    I have a 3 bed end of terrace but a reasonably big south facing (100% south) rectangle shaped roof measuring 10.5m long by 4.4m high, but a fairly steep 45 degree angle.

    House is 4 years old and came with 4 panels installed. The only info I get for them is on a tiny RCB sized screen in the fuse box and I’ve no idea how to read it… Hoping these can be kept and used with a pile of new panels.

    I would ideally like cover the whole roof in panels but don’t exactly have a huge amount of spare money. Should I borrow big and try get 18-20 panels fitted? Will I generate and use/export enough power to cover a good bit of the repayment on a 10 year loan? (2 adults, 2 toddlers, nobody home from 8am to 5pm Mon-Fri, current bills are €90/month after latest price rises).

    I’ll definitely get at least another 8 panels fitted as I can afford that for sure, but would stretch to a bigger system if financially viable. The recent news of a feed in tariff has given me confidence to invest, and I’m also hoping to add to green generation and reduction in co2.



  • Registered Users Posts: 4,157 ✭✭✭con747

    Don't expect anything from life, just be grateful to be alive.

  • Moderators, Home & Garden Moderators Posts: 4,507 Mod ✭✭✭✭graememk

    So what you have is a meter,

    You can take a reading say every month and that would be your monthly generation, eg 1000kwh today and 1300 this day next month, (or every week/day/etc)

    your roof size, 10m, panels are roughly (for the longi ones) about 1.1m x1.7 and allow 5cm between panels is 1.15, yeah you'll squeeze 18 in max, maybe 16.

    You'll prob have to start with all new panels but you should be able to sell on your old stuff easily enough.

    As for payback, get quotes, and see where it sits.

  • Registered Users Posts: 1,039 ✭✭✭silver_sky

    From experience it'll be easier to start fresh and get a quote for new panels to replace. I recently upgraded my new-ish house that included panels. They were <12 months old when trying to get quoted and I struggled, but did manage to retain them in the end.

    One thing is that the panels will degrade slightly each year which may make it more complicated mixing and I'm sure your 4 year old panels included to tick a box aren't that high of power. They probably did the minimum.

  • Registered Users Posts: 125 ✭✭alexf1

    Right, time for an update. Made contact with a good few installers, got some quotes but in the end it would have been too much for me to borrow in one lump to get the big install. I went with the Solar as a Service company, and had 16 x 400w panels fitted this morning along with 6kw inverter for €94.50 a month. I believe this is old pricing as I was quoted in October last year and was waiting on an install date since then. Scaffolding put up yesterday in a couple of hours, solar crew started at 8am today and gone by 12pm! 4 old panels removed, 3x roof vents moved down a row to make space and 16 new panels put up, wiring done to fuseboard and a very tidy inverter install in the attic. Would highly recommend them.

    There was some sun for a few minutes earlier and I was seeing 6kw on the readout. As of right now it's mostly cloudy here in west Dublin, I'm getting 700w instantaneous and I've gotten 5.44 kWh in 3 hours since it was activated.

    Looking forward to seeing my energy bills drop and some income from the FIT. I'm with SSE so should be getting €0.24 / unit. Estimating I'll be up €15/month over the year after paying the fee but let's see.

    No battery or diverter in place at the moment. Hopefully I'll get an EV in a year or two to make the most out of it.

  • Moderators, Home & Garden Moderators Posts: 4,507 Mod ✭✭✭✭graememk

    Don't forget to stick the old panels up for sale!

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  • Registered Users Posts: 125 ✭✭alexf1

    Sold already. Friend buying them at a fair price to add to his install. Could be interesting, 2 vertical on a wall and two on a shed roof. Fair play on getting that past the wife....

  • Registered Users Posts: 1,137 ✭✭✭DC999

    Welcome!! Class, you'll get great output with 6.4kWp on a South roof.

    EV wise, if you do the usual 15000kms a year, you'll save a least a grand a year on juice. Would cost €320 a year for 2400kWh 'fuel' on a night meter (cheapest rate is something like 13.5C at mo afaik). So you can do the maths on what you pay for motion lotion now to see the saving. We got a 2016 Leaf and it's amazing. It's a city car, with a city range - but perfect for us. Car tax is still €120. We save ~500 tax compared to last 1.6 petrol engine. All that helps pay for the car loan. We waiting until we were replacing the car anyway.

  • Registered Users Posts: 4,371 ✭✭✭Gerry

    welcome Alex :)

    Serious system, I didnt point out that it will do very well in winter, relatively speaking. As its pure south with very little shading

    Those old panels arent a problem on shed, she approved those ages ago. The other 2, well lets see :)

  • Registered Users Posts: 125 ✭✭alexf1

    Yep, happy with the performance over the last week. Did 37.4kWh on Tuesday!

    I have been looking at new(er) cars as I need to replace my current 2010 jalopy. I'd probably only spend €10k max, and that would get me a Leaf, but I don't think it makes sense for me. Range is a factor. It's disappointing that some will only do 80-100km on a charge now, and that will only get worse. I don't do big miles, commute is 45km per day, spend about €100/month on diesel right now. I was looking and a fill up of the 24kWh battery would be say €12 approx for 100km travelling on the high rates of domestic electricity (if I was charging at home in worst case scenario of 50c per unit). Filling at night on a low EV rate is obviously much better if you go for that, but then you get penalised for the rest of the day. I'd get further on €12 of diesel. I will revisit when I can buy a car with more range allowing me to charge it from solar at the weekend and let it last the week of commuting.

  • Registered Users Posts: 1,137 ✭✭✭DC999

    When you're ready, there's an EV forum elsewhere on Boards. Might even give a sense of the cost and range of cars.

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  • Moderators, Sports Moderators Posts: 17,897 Mod ✭✭✭✭slave1

    Those cars are coming up on 10yrs old and we're among the first EVs on the road, they didn't have massive range to begin with given battery sizes at the time

  • Registered Users Posts: 125 ✭✭alexf1

    Quick update after almost a month since install on the 1st of March. Not a great month for sunshine but I've generated 390kWh's in 27 days. Also, our BER went from an A3 rating to A1!

    I got a Smart meter installed on the 7th of March. So far I have used 56 units of my own generated power, exported 283 units and imported 130 units in the last 20 days. Doing quick sums I'm up €45 so far! (We do need to optimise our power usage as a family though, that's the next battle)

    Currently paying 29 cent/unit. If my rate goes to 45 cent/unit the exact same usage would leave me only up €34. Not sure what the future holds but my 33% discount contract ends in June with SSE. Hopefully there are some decent options available then. I will need to get a decent export price for as long as possible to help cover the repayments on the system.

  • Registered Users Posts: 2,230 ✭✭✭bullit_dodger

    Not sure how you are up €45, but you're pretty close to breaking even for march

    exported 283 units @ €0.24 unit = €67.92

    + consumed 56 units @ €0.29 unit = €16.24

    = €84.16

    So if your paying €94/month you'll be there or there abouts by the end of march in 4 days time. Bearing in mind though that March is only the 1st good month of the year. In April -> October you'll be beating March's figures unless it's a VERY miserable month.

    Best part is that in 10 years or so, the equipment is yours and your "good to go"