# Solar Panel Selection - Opinions Wanted Please



## newme (Aug 11, 2011)

Right Ive been roped into helping find out which panels and that my mum should get put on her house.
They have narrowed it down to two local installers that Ive checked as being legitimate.
Southwest facing rooftop, Cornwall, hillside, close to the sea (idk 2-3 min walk). Been asked to specifically check about possible salt problem because of this.

First option 

3.99KW, 21 panels £12,995
Changzhou NESL190 panels
£1419pa FIT

Fixtures and brackets stainless steel, panel sides aluminium, joining strip SS. 
Possibly use polymer spray to seal panels.
Drilled through tiles to rafters.

10 year guarantee on components and labour, additional guarantee to makeup difference of FIT if lower than quote.

Second Option

3.42KW, 18 panels £11,762
Suntech panels (no model number just a load of marketing specs that dont mean fuck all to me)
Sunnyboy SB3300/3800 inverter
£1160pa FIT

Tiles cut around bracket - roof not penetrated.

5 year parts and warranty on work including water ingress, etc. Modules and inverter have 5 years parts warranty.
Guarantee on salt corrosion.

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Basic questions they were coming out with was 
1 is one of these particularly superior given location (near to sea, salt problems etc).
2 Any other particular reasons to choose one over the other, barring the fact one has a higher FIT as thats fairly clear.
3 Is one method of attachment superior to the other? Can be fairly windy here at times and one guy mentioned windshear at them so there we go.

Also does any of the figures look dodgy, wrong or somehow incorrect in some way or anything look well dodgy lol.

Like to try and make sure they get the best deal considering its a fair whack to put down and they are looking to minimise bills as much as possible when they retire (next few years)

Thanks in advance.


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## newme (Aug 12, 2011)

hmmm clearly Ive posted this at the wrong time for the people who are likely to know lol.


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## ATOMIC SUPLEX (Aug 12, 2011)

I wish there was more info about this sort of thing. Do both guys install the whole thing and connect it to the grid for that price?


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## newme (Aug 12, 2011)

Yup all included it seems. Seems a pretty damn good return on investment really.


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## pinkmonkey (Aug 12, 2011)

pm Freespirit - he installs panels.


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## two sheds (Aug 12, 2011)

Have you tried R-Eco (http://r-eco.co.uk/)? It's a co-operative and the blokes I've dealt with have been great, they really know their stuff. The quote I got given was higher but that was for solar tiles which are more expensive.


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## fractionMan (Aug 12, 2011)

I only know about the small scale non-grid tied stuff I'm afraid.

My guess is the quality of the inverter is paramount.  In smaller scale installs a decent solar battery charger can squeeze 30% more juice out of the panels.


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## newme (Aug 12, 2011)

pinkmonkey said:


> pm Freespirit - he installs panels.



Ta, have done so 



two sheds said:


> Have you tried R-Eco (http://r-eco.co.uk/)? It's a co-operative and the blokes I've dealt with have been great, they really know their stuff. The quote I got given was higher but that was for solar tiles which are more expensive.



Not been the one dealing with it all just basically been asked to help research stuff and Ive done as much as I can with my starting knowledge being fuck all lol. Have had information off both installers but obviously they are in the end trying to sell their products, hence looking for independent info 



fractionMan said:


> I only know about the small scale non-grid tied stuff I'm afraid.
> 
> My guess is the quality of the inverter is paramount.  In smaller scale installs a decent solar battery charger can squeeze 30% more juice out of the panels.



Not even mentioned the inverter on the first one, Suntech appear to be the bigger company and couldnt find a great deal (well that was useful to me) regarding NSL panels. My thoughts would be Suntech panels, but being as the array smaller and therefore is gonna bring in less FIT right at a time when they wil be trying to survive on pensions there, I want there to be a bloody good reason one way or the other, not my uninformed gut feeling.


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## free spirit (Aug 13, 2011)

been on holiday, actually still am, but...


prices are too high, we'd be looking at £10.5-11.5k for the first option, which is a no brand name panel, £12,995 would be top end for a branded / european manufactured system eg sharp, Schott, Bosch etc.
what type of tiles are they? We'd only usually drill through tiles as a last resort (eg to avoid having to remove the ridge tiles), and actually cutting the tiles should only be necessary for small clay tiles (eg rosemary) or slate. We do tend to drill slate roofs though.
Yes, salt corrosion could be a factor, and I doubt the changwottzit panels would cope. Suntech are warranted and tested for salt corrosion [test cert], and are biggest manufacturer of panels in the world, so will be around to support their warrantees etc. They also come with a 10 year manufacturers warranty.
Wind could well be a factor if it's that close to the coast, wind sheer is the wind hitting the wall and then coming up potentially under the panels, and also causing vortex's around the edge of the roof which can suck the panels upwards, and come down hard on certain points. Best to leave at least 300mm around all roof edges, 500mm would be better if it's a serious concern, plus additional mounting points around the edges if it's seriously windy. Also make sure they spread the load properly across all the rafters eg by zigzagging the mounting points, or installing purlins between the rafters.
The panels used in option 1 & 2 will be the same size panels, just 3 extra on the first quote, which makes me think the first lot might be going closer to the edge of the roof than the 2nd lot, which might not be such a good idea in a windy situation.
SB3300 would be good for option b.
See if you can get them to throw in a sunny beam remote display unit so your mum can keep a check on the system more easily.


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## newme (Aug 14, 2011)

Wow amazing response, especially given your currently on holiday, many thanks 

Pitched roof cedar singles apparently is the roof type? Southwest facing in Southwest Cornwall close to Penzance. Assuming that has some bearing on the fixings.
Looking at the quotes it says the Suntech panels are bigger than the Changzhou NESL panels hence the lower size array due to space concerns. Was a quote for a 3.84KW Sanyo array but that was looking at 15k and was basically disregarded.


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## free spirit (Aug 14, 2011)

ah... cedar shingles. Erm, either method could work if done right.


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## newme (Aug 14, 2011)

free spirit said:


> ah... cedar shingles. Erm, either method could work if done right.



Frankly I thought it was slate, shows exactly how much Ive looked at the roof lol, but apparently thats the one.
Thanks, you have been incredibly helpful


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## spacemonkey (Aug 15, 2011)

Tell your parents to compare the installed cost per kWp.

First option - £3256/kWp
Second option - £3439/kWp.

They should be able to get down to at least £3,000/kWp now, and I've seen several quotes in the last few weeks getting down below the 3k mark. As freespirit says that's for chinese panels. Sanyo etc will cost more.

Sunnyboy inverters should have a 7 year warranty. Most extended warranties cost more than a new inveter, so don't bother. Plus the costs should have come down by the time they need to replace it. They will likely go pop once through the life of the system. So make sure they factor that into the payback calculations.

Still don't know why people are so obessed by payback anyway! Nobody buys any other electronics with obessive thoughts about cost deprepriaction and payback. If they did nobody would ever buy a new car! 

If you parents want to speak to someone, tell them to call the Energy Saving Trust, they have a technical team who can help with impartial advice......


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## newme (Aug 15, 2011)

spacemonkey said:


> Tell your parents to compare the installed cost per kWp.
> 
> First option - £3256/kWp
> Second option - £3439/kWp.
> ...



Yeh the cost per KW thing had come up and had been worked out. Suntech still looks better of the two based on pretty much everything except that. Could the fact were in Cornwall be related to the quotes seemingly being higher than expected?

As to the inverter, yeh Id already found out they were likely to have to replace the inverter once over those 25 years but thanks 

People obsess more on the payback from these things as well other than saving you money, the aren't doing anything useful really. Its seen more as an investment than a consumer electronic.

Lots of people do obsess on cost depreciation and payback on cars! In fact certain brands and models are suffering from people not buying brand new for this exact reason, the fact you lose thousands of pounds by driving it off the forecourt is a huge problem. Manufacturers having to produce pre-used cars as a loss leader to actually get rid of them!

Not so much for other electronics, but then most other electronics you aren't looking at £10k upwards as a starting cost.

That independent lot sound like a great other option  was the independent viewpoint I came here for lol.


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## spacemonkey (Aug 15, 2011)

newme said:


> People obsess more on the payback from these things as well other than saving you money, the aren't doing anything useful really. Its seen more as an investment than a consumer electronic.



Yeah I suppose electricity isn't _that_ useful. 

People take energy for granted.


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## newme (Aug 15, 2011)

spacemonkey said:


> Yeah I suppose electricity isn't _that_ useful.
> 
> People take energy for granted.



Currently getting electricity anyway, so the perceived difference is only that of a cost saving.
If there wasn't a National Grid, yes it would seem hugely more useful from a point of view of oh fuck nothings working without it.


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## free spirit (Aug 16, 2011)

newme said:


> Wow amazing response, especially given your currently on holiday, many thanks
> 
> Pitched roof cedar singles apparently is the roof type? Southwest facing in Southwest Cornwall close to Penzance. Assuming that has some bearing on the fixings.
> Looking at the quotes it says the Suntech panels are bigger than the Changzhou NESL panels hence the lower size array due to space concerns. Was a quote for a 3.84KW Sanyo array but that was looking at 15k and was basically disregarded.


suntech 190's are almost exactly the same size as the changzhou's, I just checked.


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## free spirit (Aug 16, 2011)

spacemonkey said:


> Sunnyboy inverters should have a 7 year warranty.


should have a 10 year warranty, but actually have a 5 year warranty as standard along with most others.

make sure the inverter's somewhere relatively cool, and give the fan a clean every couple of years though and it should last significantly more than 10 years no problem. The sunnybeam ought to help with that as well as it should help spot problems before they become inverter killers.

fwiw, we're now averaging around £11k per 4kWp system using suntech + sunnyboy 4000TL with sunnybeam, so £3000 per kWp should be easily achievable at the 3-4kWp level. The smaller the system though the higher the cost per kWp is going to be as the other costs start becoming more of a factor.


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## spacemonkey (Aug 16, 2011)

free spirit said:


> should have a 10 year warranty, but actually have a 5 year warranty as standard along with most others.
> 
> make sure the inverter's somewhere relatively cool, and give the fan a clean every couple of years though and it should last significantly more than 10 years no problem. The sunnybeam ought to help with that as well as it should help spot problems before they become inverter killers.
> 
> fwiw, we're now averaging around £11k per 4kWp system using suntech + sunnyboy 4000TL with sunnybeam, so £3000 per kWp should be easily achievable at the 3-4kWp level. The smaller the system though the higher the cost per kWp is going to be as the other costs start becoming more of a factor.



Do you install a 4kW rated inverter with 4kWp of panels?


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## free spirit (Aug 16, 2011)

spacemonkey said:


> Do you install a 4kW rated inverter with 4kWp of panels?


depends. SMA have a bit of a gap between 3-4kW with their newer TL and HF inverters, so we will install 4kWp panels on the 4000TL (actually sometimes as low as 3kWp if we need to use the dual MPPT), and limit the output of the inverter to 3680W to stay inside the G83/1/1 16 amp limit.

We also install upto 4.5kWp of panels on the 4000TL with the ouput limited to under 3680W AC to get the maximum out of the <4kW FIT boundary, or even upto 5kWp if it's split over east/west roofs or something similar. Far too many companies still thinking the FIT boundaries relate to the peak DC rating of the panels, and offgem refusing to issue firm guidance to clarify it, but if you dig into the definitions then it has to be the peak AC output of the inverter.


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## lopsidedbunny (Aug 16, 2011)

Wow I have to say that I am impress by the level of info here and I won't pretend to understand the quotes mention but I do think depending on the area of the roof being covered £11k a bit on the steep side. I myself am south facing but in London with the modern day 1980s one side roof but yet measured. I had ask a solar company to give me a quote but I suppect I in for the hard sale as nothing turn up yet. Could someone give me a rough guide in finding out? I want one of those day time night time solar panels type that I hear about... but I have been told by an electrical engineering expert that the energy you get from the panels is enough to light a light bulb so that's why I querying the £11k price tag. Maybe you have a bigger area to cover etc... Another problem I have in my area is thief. A lot of copper and Iron road grills are going missing in the area I live, so the solar panels a likely target to a victim of these thief?


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## free spirit (Aug 16, 2011)

day / night panels?

the only panels I know of capable of operating at night are some panels that are used in combination with a heat pump to generate heat for the house / hot water, as they extract heat from the air surrounding the panels. PV panels that generate electricity operate from light only, and therefore can not generate electricity when there is no light, though some are better in very low light conditions than others.

if you tell me your roof dimensions I could give you a ballpark figure you should be asking for.


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## spacemonkey (Aug 17, 2011)

free spirit said:


> depends. SMA have a bit of a gap between 3-4kW with their newer TL and HF inverters, so we will install 4kWp panels on the 4000TL (actually sometimes as low as 3kWp if we need to use the dual MPPT), and limit the output of the inverter to 3680W to stay inside the G83/1/1 16 amp limit.
> 
> We also install upto 4.5kWp of panels on the 4000TL with the ouput limited to under 3680W AC to get the maximum out of the <4kW FIT boundary, or even upto 5kWp if it's split over east/west roofs or something similar. Far too many companies still thinking the FIT boundaries relate to the peak DC rating of the panels, and offgem refusing to issue firm guidance to clarify it, but if you dig into the definitions then it has to be the peak AC output of the inverter.



Yeah I agree with your second paragraph, it's very unclear, I've spoken to Ofgem about this myself.


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## free spirit (Aug 17, 2011)

spacemonkey said:


> Yeah I agree with your second paragraph, it's very unclear, I've spoken to Ofgem about this myself.


it's fairly clear if you dig down into the definitions, and realise that in other contexts eg G83 / G59 connections terms, the SSEG unit specifically refers to the inverter, not the panels, and as the meter is measuring the AC output, and the payments are made based on the AC output then it logically must refer to the peak AC output.

TIC and DNC also always refer to the AC output of the system in all other circumstances, yet probably because PV system sizes are usually described by their peak DC rating for ease of comparison, everyone seems to have assumed it must be referring to the peak DC rating of the array and not bothered actually checking if this actually makes any sense or not.


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## spacemonkey (Aug 18, 2011)

free spirit said:


> it's fairly clear if you dig down into the definitions, and realise that in other contexts eg G83 / G59 connections terms, the SSEG unit specifically refers to the inverter, not the panels, and as the meter is measuring the AC output, and the payments are made based on the AC output then it logically must refer to the peak AC output.
> 
> TIC and DNC also always refer to the AC output of the system in all other circumstances, yet probably because PV system sizes are usually described by their peak DC rating for ease of comparison, everyone seems to have assumed it must be referring to the peak DC rating of the array and not bothered actually checking if this actually makes any sense or not.



Sorry I meant it was unclear/confusing for customers looking at installing PV. Installers should know better really.

I don't know why I'm surprised. I had installer (not a salesman) tell a customer yesterday that SAP doesn't take into account any generation past 4pm. So the massive shadows cast by the customers trees wouldn't really affect his annual output predictions.


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## free spirit (Aug 19, 2011)

tbf, sap probably doesn't as it's lowest shading range is for none or very little, which it states as being <20%, and post 4pm shading would place it in the under 20% shading bracket. The shading therefore wouldn't impact on the SAP performance estimates, but would impact on the real performance of the system.

One of the many reasons why SAP isn't fit for purpose, and we don't use it for our proper performance estimates, only tucked away at the back of the quote as a for comparison bit with an explanation of why it shouldn't be trusted. We do 3d shading models, matched with geographically specific hourly output estimates for each month of the year to produce precise estimates of the shading impact on the annual output of the system, for the precise roof angle, orientation, and the relative efficiencies of the panel and inverter combination, then back them up with a -5% performance guarantee (dependant upon the actual insolation levels relative to the 10 year average.

SAP really should be scrapped and replaced with a requirement for companies to guarantee their performance estimates. It's possible to do this with high levels of accuracy, and it pisses me off that REAL forces us to use such an inferior method of producing a rough guestimate of the average performance of an average system averaged across the entire country just because it's fairly idiot proof. Accuracy should trump idiot proofing the system IMO.


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## spacemonkey (Aug 19, 2011)

free spirit said:


> tbf, sap probably doesn't as it's lowest shading range is for none or very little, which it states as being <20%, and post 4pm shading would place it in the under 20% shading bracket. The shading therefore wouldn't impact on the SAP performance estimates, but would impact on the real performance of the system.
> 
> One of the many reasons why SAP isn't fit for purpose, and we don't use it for our proper performance estimates, only tucked away at the back of the quote as a for comparison bit with an explanation of why it shouldn't be trusted. We do 3d shading models, matched with geographically specific hourly output estimates for each month of the year to produce precise estimates of the shading impact on the annual output of the system, for the precise roof angle, orientation, and the relative efficiencies of the panel and inverter combination, then back them up with a -5% performance guarantee (dependant upon the actual insolation levels relative to the 10 year average.
> 
> SAP really should be scrapped and replaced with a requirement for companies to guarantee their performance estimates. It's possible to do this with high levels of accuracy, and it pisses me off that REAL forces us to use such an inferior method of producing a rough guestimate of the average performance of an average system averaged across the entire country just because it's fairly idiot proof. Accuracy should trump idiot proofing the system IMO.



Yeah SAP isn't great, that's why I assumed it wasn't detailed enough to account for that level of accuracy. I was advise people to ask their installer for a more detailed prediction.

What software do you use to produce the shading models? Sounds like you offer an excellent service, far better than some of the new boys on the scene. I wouldnt be happy agreeing to drop £11,000 on a microgen system after only a 2hr consultation with a salesman, but many people do.

Have you spoken to REAL about their SAP requirements?


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## free spirit (Aug 19, 2011)

we use google sketchup to produce a 3d model, then run it's inbuilt shading modelling for each our of the day through the year (or at least for the hours that we'd expect shading to be an issue), predict what percentage performance losses we'd expect for that hour, stick it into a spread sheet we've developed that compares it with the proportion of energy output to expect on average for each hour (taken from a local weather stations data), to produce the overall shading losses, then plug these losses in to the PVGIS software along with the precise inverter, panel and cable losses, to produce an accurate prediction for that few KM2 grid square.

Alternatively, we have a fisheye lens shading tool that allows us to view the shading through the year from the site, but this only works if we can access the roof on the site visit, and isn't as precise, but can be good for situations with shading from trees that can be a bit hard to model accurately.

Where there's no shading obviously we short circuit this, and if we know it's going to be minimal and we've already modelled similar shading situations then we'll guestimate it, but still back it up with our guarantee.

feedback so far seems to be that our predictions are accurate, and probably a slight underestimate, which is as expected as we er on the side of caution a little.


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## Bingo (Aug 5, 2014)

Trying to persuade my Dad to have a couple of quotes.... they've got a huge roof area round the back of the house but he says its no good as its not facing directly south.... I reckon it faces roughly southeast.

Are there decent companies who will come and have a quick look?


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## Bingo (Aug 5, 2014)

There are a few biggish trees about 25m away as well


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## free spirit (Aug 5, 2014)

Bingo said:


> Trying to persuade my Dad to have a couple of quotes.... they've got a huge roof area round the back of the house but he says its no good as its not facing directly south.... I reckon it faces roughly southeast.
> 
> Are there decent companies who will come and have a quick look?


You're in the Leeds area aren't you?

Happy to have a look and work up a quote for it, this is me www.leeds-solar.co.uk

As a rough guide, South East facing systems produce approx 6% lower than a perfect south facing system, so for a big roof it's very likely to be viable.


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## Bingo (Aug 5, 2014)

Aye but me grumps are in Calderdale... gonna have to try and work him round to the idea a little bit more but think its doable, got any links to how much he might earn from selling excess, or a rough calculator website to put details into? Actually will check your site first. Ta


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## free spirit (Aug 5, 2014)

we cover out well past calderdale


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