Got a quote. Any good?!

ickleMouse

Hello experts,

Looking into PV despite the low payback and wondered if I could ask anyone with more experience to critique a quote I've got? I'm on the north bank of the Humber, 45 degree roof and 20 degrees from South. A capacity of 3.92KWp with a shading factor of 0.9 used to give estimated annual output of 3,097kWh. The kit spec is;

14 JA Solar Smart Module 280W Cypress 5BB Monocrystalline All Black Solar panels.
1 SolarEdge 3680W 1ph HD-Wave, Wi-Fi Solar Inverter (12 yr war).
Schletter - Pan Tile On-Roof Mounting Kit
All cabling, switches and meters.
Roof survey
Scaffolding and roof access
Full installation and commissioning.

A little over £6k inc. VAT.

They quoted estimated annual savings of £515 which I think probably needs a pinch of salt applying to.

They also quoted a string style installation with the same panels but with a Solis 3.6k 4G Dual MPPT 1ph inverter instead for £5k but claimed the non-string configuration will increase the yield by up to 20%.

Appreciate anyone who could help evaluate and offer their $0.02.

Many thanks.

pinnks

Welcome to the forum.

SE is good as each panel is managed separately and the monitoring software can tell you what each panel is doing. It is more expensive and particularly good if you have shading at particular times of the day from other houses, trees, chimneys etc. If you don't, then the extra yield is more marginal and it probably comes down to personal choice.

This is a good time of the year to see what is probably the maximum impact of shading as the sun is very low in the sky. If you can it's worth taking a few pictures of the roof in question every hour or so on a nice sunny day to see how any shadows track over the roof. You can then guess how that might be when the sun is higher in the sky in spring, summer and autumn.


Folk here will also ask for details. For instance, my main array is facing WSW and I spent a lot of time studying the chimney (search on my user name and shading and you find some posts on the issue). However, because the roof doesn't come into direct sun until the sun peeks to the west of south at about lunchtime, by which time the shadow is gone, its impact is irrelevant. I generate a couple of hundred watts in the morning, so knocking say 50% off because of the shadow is 100W or so. If that persists for 3 hours the cost is 0.3kWh. However, once the sun comes round and the panels get direct sunlight the generation jumps to 3000W or so. If that came into shade then the impact is massive.

However, at certain times of the year next door's roof casts a shadow for a while and at this time of the year another neighbour does the same mid afternoon. Neither is an issue in the summer. Would SE have been beneficial for me? Perhaps but probably marginal on that roof.

Move to my other array facing SSE and the position is different. It gets some winter shading too but that chimney casts a shadow from about 14:00 and kills production, especially in the summer, even when only one panel suffers about 5% shading - production drops by up to 90%!. Costs me about 3kWh per day on a sunny summer day, so perhaps 3 x 150 = 450kWh per year at whatever FiT you have - about £85 per annum for me perhaps at just under 20p per unit FiT. Not enough to warrant rectifying but SE would have been worth it at the outset had I known then how the shadow would impact a string inverter.

As for the quote, feels a little high but others can comment better than I and the annual saving looks overly optimistic. Estimated generation looks reasonable for just off south.

Unless you are a high-user of electricity you'll probably save about £120 from the PV electricity you self-consume and to that you can add the FiT but at 6p or so per unit or whatever it is now (generation plus deemed export) that would add about £180, so perhaps £300 to max £350, not £515.

You will become more energy conscious - I have reduced my imported electricity by 70% since getting interested in PV (about 50% when you add my self-consumption) so that will generate extra savings but you could do that without spending a penny on PV and investing instead in ultra low consumption devices.

Don't get me wrong, I am a PV fan but with the low FiT the economics is marginal and installers need to bear some of the pain and give you keen prices...

HTH:beer:

Martyn1981

I'm with pinnks, check for shading now, especially as you have a relatively steep pitched roof which favours lower sun angles than shallow pitched rooves [Note - steep rooves are brilliant, less gen in the summer when you'll have too much, and more in the winter when you need every watt.] Solaredge is brilliant but costs more, so have a little think about shading.

At the very least I'd have thought you could ask for £6k, 300Wp panels, and they bump up the warranty from 12yrs to 20yrs (about £100).

Will the roof be maxed out at 14 panels, if not then consider adding more PV. The inverter capped at 3.68kW means you can go bigger without permission and it can cope with up to 5.7kW.

Zarch

Just for comparison, I had a SE 3680 inverter with 17 x 300w JA panels (with optimsers) spread over 4 different aspect/roofs for £6200 inc vat the other month.

So I think there is wiggle room in your quote for negotiation perhaps?

As Mart says though..... what is limiting you to 14 panels? The roof size or the installer saying 14 x 280 = 3920?

As you can see from my install, I have 5100 worth of panels on a 3680 invterter because its the limit of the inverter that counts, not the number of panels. Yes, in summer I will top out the inverter at 3680, but on days like this month, the higher potential generation from having more panels/capacity really helps when you're struggling to get 500 watts on indifferent days.

Hope this helps.

ickleMouse

Thanks all for taking the time to reply - very much appreciated.

The roof is 154 degrees SE and I work from home so will be taking advantage of day time generation. The .9 shading came from the presence of mature trees in a neighbour's garden but in reality the shadow they cast is pretty low down on the roof and watching during the day, I doubt they would impact very much...of course they could grow a little taller in time.

Thanks for confirming the quote seems a bit high with an optimistic benefit. That and the comparable installation from Zarch will be really useful in going back in to battle.

Thanks again :-)

JKenH

I would endorse everything Pinnks and mart have said to date. My system was designed in May/June when I could not imagine any shading but now with the sun so low in the sky it is really suffering from trees casting their shadows. So, as already said, a great time of year to design your system.

I wish I had gone Solar Edge but didn’t do enough research at the time. The extra kwh generated may not seem much and it probably wouldn’t have been a financially sound choice but I follow my PV generation very closely and also that of others and the frustration of losing out on available solar PV would, with hindsight, be enough to swing it for me. It might just be me but whenever I buy anything I always look at cost then afterwards wish I had spent a bit more and got the best. You will have your panels for the next 20 years so get it right first time.


Our 7.8 kwp solar installation has BTW worked out at under £1/wp installed.

We have only had our panels 4 months or so but as Pinnks says we have have become extremely conscious of how we use our electricity and you may find in a years time that you have saved more than was estimated but much of that will be down to lifestyle changes. We happen to have immersion heaters and with an IBoost at this time of year mop up every spare kwh produced. We also have a 1.25kw 1.2 litre insulated kettle which offers us great savings compared with a 3kw fast boil 1.7 litre one. We don’t ever see 3kw of PV this time of year but if the sun is shining have 1.5kw from 10am to 3pm.

If you are out during the day or don’t have immersion heaters then FiT and Export payments (approx6.6p/kwh) will be more important to you than the self consumption (around 14p/kwh or 7p if you are displacing E7 usage). In that case it may be hard to make a case for Solar Edge.

PS. sorry that was written before your comment about working from home. So I would say go Solar Edge.... and get a low wattage insulated kettle as you will always have a brew on the go.

Merlin139

Just spent 10 minutes looking at the cost of what you are getting and I would say that to a trade buyer you could get the inverter, 14 optimisers and 14 panels for around 3.2K so there is still quite a bit of profit in the quote.

I paid under what you are paying for my Solar Edge system 4.5 years ago and it included an Iboost for my hot water. That has used 5.3 MW out of the 18.5 MW that my system has produced.

I am at home most days and try to use as much free electricity as I can.

Exiled_Tyke

ickleMouse wrote: »

Thanks all for taking the time to reply - very much appreciated.

The roof is 154 degrees SE and I work from home so will be taking advantage of day time generation. The .9 shading came from the presence of mature trees in a neighbour's garden but in reality the shadow they cast is pretty low down on the roof and watching during the day, I doubt they would impact very much...of course they could grow a little taller in time.

Thanks for confirming the quote seems a bit high with an optimistic benefit. That and the comparable installation from Zarch will be really useful in going back in to battle.

Thanks again :-)

Even a little shading will have a serious impact on the generation of a panel and for a non-Solar Edge installation, every panel in the string will then be reduced to the performance of the shaded panel. Solar Edge allows each panel to work independently and not be affected by the performance of the other panels.

pinnks

Take a look at the impact of shading on my smaller array in this document https://www.dropbox.com/s/2k06xp8bjehyx32/More%20on%20the%20impact%20of%20shading.pdf?dl=0