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Three questions on a new solar panel install

edited 6 October 2017 at 2:08PM in Green & Ethical MoneySaving
6 replies 1.9K views
digbydogdigbydog Forumite
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edited 6 October 2017 at 2:08PM in Green & Ethical MoneySaving
I've had two quotes so far one from EON and one from SolarCentury/IKEA.

The EON quote mentions 'SolarEdge Optimisers' the SolarCentury/IKEA ones does not mention any optimisers. Is that a significant difference?

From what I tell batteries are still expensive and at the moment are not a cost-effective option. I'm of the opinion that will change in the next three years or so. Is it, therefore, important to get an inverter now that will work with batteries in the future.

Finally, the Which report on solar panels talked about not putting the Inverted in the loft due to heat potentially limiting its effectiveness. Is this a significant factor and should I insist on it being put in my garage which is obviously much cooler.

The ramblings below are my experience so far with getting the quotes.

For the EON one, a guy came around and spent about 90mins checking the existing electricity usage, the angle of the house, the angle of the roof and any shading at different times of the year. Seemed quite thorough but I'm fairly certain he was more salesman than surveyor but even as a salesman he was not excessively pushy. I'm in Bristol, and according to the quote the roof faces south-south east (-31 degrees from South), has a roof angle of 39 degrees, shade factor of 0.86 (not sure if that is good, bad or average). I wanted black panels for aesthetic reasons, and he suggested what they call their 'Classic' package which I think means not the cheapest and not the most expensive. He said that I could have the following system for £8,895.00 including VAT

20 JA Solar PV Panels
SolarEdge Inverter
SolarEdge Optimisers

This would have an installed capacity of 5.90kWp and an estimated annual output of 4,795kWh. I suspect the first figure is the theoretical amount generated and the second the actual amount.

SolarCentury/IKEA did one based on Google Earth, although if I want to take it further, they will send a surveyor around at the cost of £125.

Their quote was for a 16-panel system, although in a subsequent phone call they said they could quote for a much bigger system as I've got the space available.

16 JA Solar 280W Mono
Solax hybrid inverter

The cost of this system was £6,542.00 (which includes the cost of the full survey).
There was also an option with SolarCentury to add an LG Chem 6.5 battery at the cost of an additional £3,440.00.

I suspect small local companies would be cheaper but I've rung several over the last 10 days, and they take messages and then I never hear from them again. My thinking is that if they cannot get organised enough to follow up on leads, then I don't trust them to do a very good job on my roof.




  • Martyn1981Martyn1981 Forumite
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    Part of the Furniture 10,000 Posts Name Dropper Photogenic
    Hiya Brendan, let's see.

    SolarEdge is a different type of system, I had it originally on my WNW system, and have since had it retro-fitted to the ESE.

    Rather than having all panels in a string where shade on one might effect the performance of others, SolarEdge connect each panel to a power optimiser (PO), and then the the PO's are connected in a string to the inverter. This means that each panel operates individually maximising it's potential.

    However, it does mean you have more components on the roof that could go wrong, so may need access. Their inverters are extremely efficient, about 99% and come with a 12yr warranty, but an extension to 20yrs is cheap, and most installers probably throw that in.

    Batts are too expensive at the moment, in my opinion, but lots happening. So you might want a battery friendly inverter, but you could also choose batts that are on the AC side, so have their own inverter and operate separately, so it's not a crucial decision, but worth a ponder.

    This thread has loads on batts, but as you say, probably worth waiting 2 or 3 years to see what happens, or for a scheme to pop up, as 'things' get launched every so often.

    On-grid domestic battery storage

    Inverter position. Worth thinking carefully, but again not crucial. Your loft will probably be cooler after PV as the sun won't hit the slates/tiles directly, but a cooler location is usually more sensible. So a garage sounds better, also if you do get a battery friendly inverter, you may want to co-locate them later on.

    Performance wise, take a look at PVGIS, see section 5 of the FAQ's (link in my auto sig). That will give you a very, very good guestimate of average annual generation. Shading wise, start taking a look at your roof now, as the sun is getting lower, this will help guide you on how bad the shading may (or may not) be. Also if your roof is very big, which parts to use or not use. SolarEdge can't eliminate shading, but by managing it's impact on un-shaded panels, will solve most minor issues.

    Size wise, I'd suggest going big (within reason). 5.90kWp is a good size and would help to future proof you for batts, maybe an EV etc. But for now, obviously the more you generate the more you'll export, law of diminishing returns. But, you can't get the FiT subsidy for extensions, so best to go big straight off, than to ponder it later.

    For 5.9kWp, even with SolarEdge I'd have thought £7k was do-able with some minor haggling. A lot of the cost is fixed (overheads, labour, scaffolding, inverter, paperwork, profit etc) so some extra panels and roof railing is actually not that much.

    If your system can generate more than 3.68kW, then you'll need permission from your local DNO (district network operator) or have an inverter set to cap generation at 3.68kW.

    Regarding size and generation. PV is rated at the kW's it will generate at p peak, based on about 25d C. So 5.9kWp is 5.9kW peak, but obviously generates nothing at night, less when hot, possibly a bit more when hot etc etc. So you also need to see generation estimate, as mentioned earlier. I've just tried PVGIS, stuck a few random pins in Bristol, with settings of 5.9 for PV size, 39d for roof pitch and -31d for orientation, and got roughly 5,600kWh's of generation per year.

    I think I've bored you enough, so have a look at the FAQ's then chat away with us all.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • EctophileEctophile Forumite
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    Just to clarify, kWp and kWh are completely different things.

    kWp is the peak power you will get out of the panels on a sunny day, with the sun shining directly on the panels. At other times of day, or if it's cloudy, you may get a lot less than the peak.

    The kWh figure is the total units of electricity you can expect to get over the course of a year. One kWh is one "unit" of electricity, as measured on your bill. So the 4,795kWh figure means your export meter should read about 4795 at the end of the first year.
    If it sticks, force it.
    If it breaks, well it wasn't working right anyway.
  • pinnkspinnks Forumite
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    Just to add in terms of inverter location, as Mart says the panels will take the direct heat out of the sun, not least because your panels will be on the south-most-facing roof. My loft used to be stifling in summer, acceptable to wander around in the shoulder months and cold in winter. Now it is shoulder-month temperature in summer, cool in shoulder months and the same in winter.

    I am content with my loft-based inverters but have no way to judge whether I would get better performance with them placed elsewhere (not sure where that could realistically be for me). I guess you pays your money and takes your chance...

    I am not that wise on shading factors but at 0.86, or 86%, that might suggest 14% average expected shading over the year. While that may not sound much (I recall less than 10% being mentioned when I was planning mine), don't forget that absent SolarEdge type technology one panel getting shaded will hit the whole string and as most string inverters have only two strings that is about half your capacity. When the shadow of my chimney hits the corner of one panel I lose 90% of production. So, look long and hard at the shading data and ask on here whether people with more knowledge than me think SolarEdge is worth the extra money. My guess is that it probably will be.

    Best of luck.:beer:
    Wiltshire - 5.25kWp
    3.5kWp: 14 x Phono Solar 250 Onyx, Sunny Boy 4000TL, WSW 40 degrees, June 2013
    1.75kWp: 7 x Phono Solar 250 Onyx, Sunny Boy 1600TL, SSE 45 degrees, March 2014
  • Merlin139Merlin139 Forumite
    5.6K Posts
    I had a 3.975 Kw system installed in May of 2014. I suffer from around 10% shading because of next door being at an angle to me and slightly elevated. I opted for a SolarEdge system and have not looked back.

    If you have any shading then it has to be the SolarEdge option. It effects each panel individually instead of taking out the whole string.

    I have a garage attached to the side of my house so opted for the inverter to go in there. So much cooler and easier to read than going up into the loft.
    3.975 kWp PV SolarEdge System South Facing 10% Shading Installed 21 May 2014 Located in Mid East Yorkshire.
  • gefnewgefnew Forumite
    194 Posts
    Part of the Furniture 100 Posts
    Hi Brendan
    Sma Uk have a design app that you can download and put your details in and a range of different panel types to help to get the optimal configuration
  • edited 7 October 2017 at 6:54PM
    ASavvyBuyerASavvyBuyer Forumite
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    edited 7 October 2017 at 6:54PM
    We went with SolarEdge & Optimisers because we get gradual shading in the winter from the mountain we live on. Also, we noticed that most PV panels have a tolerance of +/- 5% on their rated output. Therefore, without optimisers a whole string can be limited to the worst performing panel; but with optimisers you get the maximum output from each individual panel. The other benefit, is that you can monitor each invidual panel on the web interface, in case of any problems.

    We also had the inverter installed in the garage under the bungalow, where it is always cool. Use to work with electronic equipment/computer servers, etc and they were always installed in a cool place to extend their life. Even if a piece of electronic equipment states it can work upto 40 or 60 degrees C, it is always better to place it in a cool environment. It is also much easier to read the display in that location, rather than up in the loft.

    If having PV installed now, we would go for the maximum size systems we could fit on our East & West facing roofs, but still have SolarEdge + Optimisers and again have the inverter installed in the garage.
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