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Installers that fit larger output panels (650w, 700w)

  • 10-11-2022 5:08pm
    Registered Users Posts: 355 ✭✭


    do any of you know of installers that will fit larger output panels in the veil of 650w, 700w etc.

    I have a south-facing 3-bed semi. Due to the smaller space and limitations with a front apex, I would only squeeze in 2.4kwp using standard size 6x400w panels. There is no option for a ground mount etc. So if I get solar, this front south-facing roof is all I have.

    I took measurements of the roof space and drew it out on a scaled drawing. Then I accounted for the 50cm edge left and bottom and a 15cm gap for the ridge.

    Taking dimensions of various larger panel specs you find online, I overlaid rectangles on this roof space to see if I can get a higher kwp. It turns out it is completely possible to squeeze upto 4.1kwp of the smaller space if the installer can supply and fit larger spec panels in the veil of 650w and 700w. Thats a 70% improvement on a 2.4kwp install.

    Attached here is a version of that diagram with Bluesun panels where I was able to slot in 4x700w and 2x650w, totalling 4.1kwp. Those types of 650w/700w panels would also work fine on a single string using optimisers given the variance is within 25% above 650.

    Just curious if any of you have been in similar scenarios or know (or are) installers that would be flexible in this regard. I've received a number of "NO" responses from several installers that only what to fit their standard 3xx or 4xx panels.


  • Moderators, Home & Garden Moderators Posts: 5,004 Mod ✭✭✭✭graememk

    No idea on installers, But what your actually asking is.. Complicated. other than them panels being huge, (think shipping, transport, cost, etc)

    The main issue is how they will be connected, I dont have the data sheets but if they were all connected in one string, the 700's would be pulled down to 650.

    2panels is usually too small for a string, 4 usually the mininium. Micro inverters could be used, but finding one big enough could be an issue.

    With people being so busy. Why go down the bespoke route.

  • Registered Users Posts: 1,231 ✭✭✭DC999

    Yep, I suffer that too few panels on a string. We can only fit 3 panels so string only starts to produce well after the other roof is producing. So at times it 'wakes' 3 hours after the other string. Meaning we lose output. Better that nothing for us (as in better we have panels on that roof), but still not what I expected output wise.

    Installers are sooooo busy now, anything not standard will cause you headaches. I’m saying that with the scars on my back!! Fill the roof with what you can get the installers to agree to.

    When you say South is all you have, are you semi detached? If so you’ve an E or W too? E will give morning sun, W evening sun. Someone is doing a large N facing. Supposed to produce 50% the S output. So even N can produce.

  • Registered Users Posts: 355 ✭✭cormacl

    Well getting 4.1kwp instead of 2.4kwp is the reason. If I'm going to fork out a min of 8k or more on an install, I'd like to get the most I can on the roof space I have. There's lot of houses in this country like mine.

    I was also told that optimisers will do the job in combining all 6 panels on the one string, no differently to how a chimney shading etc would cause some panels to perform worse than others. Those 650w panels have a peak output of 92% of the 700w panel peak. So that is supposed to be where optimisers would work fine. Worst case, it could be done as 3x700 and 3x650 on two strings with each of the strings generating the adequate min voltage for the inverter inputs.

    On the size, I get the argument but surely this is solvable in this day and age. Below I put the mockups of the panels alongside a typical 410w panel. That to be seems to be quite solvable for logistics.

  • Moderators, Sports Moderators Posts: 18,130 Mod ✭✭✭✭slave1

    I'd question PV altogether if costing €8k for 2.4kWp, it will never pay back.

    My DIY install this year was with 455w panels and they were 26kgs but it wasn't the weight it was the size, any breeze and minimum 2 to handle and they flex like crazy at larger dimensions

  • Registered Users Posts: 1,395 ✭✭✭Big Lar

    I think you should be looking at 250-300w panels or something like that, I could fit 10 of these on your roof which would get you 3.5Kw

    Economies of scale is going to hit you as the smaller panels will cost more on installation between brackets and what not, then the cost of KW per sq mtr will also be higher with the smaller panels

    If I still smoked that would be the back of a fag box below

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  • Moderators, Home & Garden Moderators Posts: 5,004 Mod ✭✭✭✭graememk

    Quick q, have you a link to them panels.. would they be bifacial ones?

  • Registered Users Posts: 4,342 ✭✭✭Padre_Pio

    Surely 650 x 6 is the best option? You're only losing 200W (lets face it, you won't miss it) and you avoid the issues of mismatched panels.

    Is the 50cm to the edge rule gone in the last few weeks?

  • Registered Users Posts: 355 ✭✭cormacl

    Big Lar,

    I took the specs of that Q-cell and then rendered the shape. Below is the best arrangement I could get with 9x350=3150kwp, ~1kw less than the 4.1. It's not bad but still its not 4kw.

    I had another Chinese panel in earlier renders that was a quite narrow 410w panel that worked well getting to 3.6kwp. But it seems the issue here is that installers are going to only work with their standard parts. You really need to fire a few larger spec panels in to get the 4

  • Registered Users Posts: 355 ✭✭cormacl

    DC999, it's semi-detached, south-facing. The north side has got three velux windows for the attic extension. There's no east or west roof. I do have a rear extension that is East-West but its heavily shaded bewteen 11-1pm and also has 4 velux windows to its name and just not worth the effort.

    And the very thing you mentioned on string size was why I was recommended to put all panels on the one string with optimisers. The guideline was that if the weaker panel + 25% matches or exceeds the stronger one, the optimisers will do a good job.

  • Registered Users Posts: 1,395 ✭✭✭Big Lar

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  • Registered Users Posts: 355 ✭✭cormacl

    I also modelled 650x6 as shown below. But the optimisers would still be there as the top right two will suffer a bit because of shading from the chimney. It's a low chimney but nevertheless will cause some shading and the bottom right panel might suffer a bit early morning from the eastern light being blocked by the front apex.

    That 50cm edge AFAIK is still there and on the guideline doc you get from the SEAI.

  • Registered Users Posts: 355 ✭✭cormacl

    I was quoted €9500 for a 2.4kwp install, no battery. All I'd get back in grant would be €1900. So €7600 in total. That was a ridiculous price obviously and I backed away.

    If I could pay 8k for 4kwp. I'd get €2400 grant back, bringing it to €5600. That would be workable in my mind as something that would recover cost in about 6 years. I would not need a battery to start. I'd be happy to use what I can and get FIT for the rest. Adding a battery later on would be the preference.

  • Moderators, Sports Moderators Posts: 18,130 Mod ✭✭✭✭slave1

    €930 saving a year! I don't have half that and I've a 14.7kWp setup

  • Registered Users Posts: 1,224 ✭✭✭Galego

    I tried few installers for those bigger panels and nobody took me on. It does make sense to be honest why they didnt. They have plenty of business right now and those panels are very heavy and flexy to handle up in a roof.

    Good luck in finding anybody who is willing to fit them for you.

  • Registered Users Posts: 355 ✭✭cormacl

  • Registered Users Posts: 5,871 ✭✭✭SouthWesterly

    Ive come across a company on FB who will sub contract out the various aspects of the work. They might suit you if you go the semi DIY route

  • Registered Users Posts: 1,224 ✭✭✭Galego

    Go for the smaller panels and see if they could fit more than what you think. With the bigger ones you may not even be able to fit 6. Think the panels have a small gap (mm) between them.

  • Registered Users Posts: 355 ✭✭cormacl

    That apex edge you see there is the end of the roof slate. So the grey section is the gully and then apex. So its got the space.

    As for smaller panel sizes, I tried all kinds of variations and the 4x700 and 2x650 are still the best option thus far. You can see the 350w setup I tried earlier based on the panels suggested by Big Lar.

    There was one config I did with 410w narrow panels and they did really well if you went a bit creative on the left "50cm" edge but again... you have to find an installer that will source such panels.

    So its going to boil down to it being an installers market doing what they want and screw the customer. It should be called the "Photovoltaic Tiger"

  • Moderators, Home & Garden Moderators Posts: 5,004 Mod ✭✭✭✭graememk

    Suspected so, they werent big enough to be true.

    Bifacial panels are "double sided"

    Great for ground mount, but no real benefit on a roof mount. Let me dig up a video from will prowse.

    Yes they are bigger, and will output more than the standard 400 w ones but likely not 700w

    The mono version is 585w by the looks of it. (Still a beast of a panel)

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  • Registered Users Posts: 355 ✭✭cormacl

    I knew they were bifacial but understood the 700w specs to be for the front side and the additional performance rated on the light leakage into the underside.

    Even from the specs, they show this going to 875W best case.

    Am I correct on this?

    That said, the 650w is definitely not bifacial and then should be taken as a 6x650 = 3900kwp

  • Moderators, Home & Garden Moderators Posts: 5,004 Mod ✭✭✭✭graememk

    Oh yeah, your right, the 700w is the front face.

    Don't think you'll get much more added performance from it.

    But as you've found out, getting them is a issue, not even getting them fitted

  • Registered Users Posts: 355 ✭✭cormacl

    I will likely have to wait this out unless I do manage to find a smaller installer that is flexible.

    But I think also, half this issue is that the uptake of solar is still very low despite the demand on installers. If it picks up, these kinds of low yield 2.4kwp installs will not fly any longer, especially when there are so many.of these semi-D roofs that can't take 14 panels.

    That's the hope :)

  • Registered Users Posts: 1,231 ✭✭✭DC999

    You could DIY the rear extension that is East-West. Put a micro inverter on which would sort the shading issues. Under a grand and you’ll have some solar. Tbh I didn’t realise it was as easy as I would have done that on my flat roof extension. I’m gonna look at this too for family members. Random Renewables Thread - Page 11 — - Now Ye're Talkin'

    Look, you’re 100% right. We should be filling every viable nook and cranny with solar. But we’ve only a small number of installers. And they are gonna cherry pick at the mo (as I would if it was my business and I was turning people down). As we move to electrify our worlds (electric heating, EVs….), you’re bang on that small systems are not gonna help a whole pile.

    Up to a year ago installers were likely somewhat busy. They had to spend a lot of time convincing people solar was a runner. This year they are off the charts and beating potential customers away. The crowd who did ours went from 1 crew to 3 afaik.

  • Moderators, Sports Moderators Posts: 18,130 Mod ✭✭✭✭slave1

    Maybe it's been mentioned, you will need additional rails too, standard is two but those beasts will require at least 3, maybe 4

  • Registered Users Posts: 63,640 ✭✭✭✭unkel

    That spec sheet shows a panel efficiency of over 25%. Unless I can see some proof of that, I would take that figure with a pinch of salt.

  • Registered Users Posts: 355 ✭✭cormacl

    Unless this is part of the claim of being N-type instead of P-type. The 700w panel is also shingled and they claim that also performs better.

    I wasn't specifically seeking these panels or brand as such. It was more a case of finding a variety of capacities and sizes and these two met the target of reaching 4kp on the space I have.