Solar Panel Quote

DiggerUK

The array the OP is considering to have installed is 8.9 KW, which would require 27(?) x 320 W panels. The are claimed to have a 20% efficiency.  If the OP is expecting the plated 8.9KW to be produced they could be in for a disappointment, especially as degradation of solar panels is a given known over time and will reduce the power output.
They don't appear to have any producers warranty/guarantee so they will need to carefully check the suppliers warranty/guarantee insurance and who it is with.

The same due diligence for who is responsible for the warranty/guarantee on the inverter needs to be clarified 

The costs for insurance on such installations is fairly bog standard. This site I found representative.

All in all I don't see much due diligence from the OP with regards to the  downsides of this project. MSE is after all a money saving site and this project looks overpriced for what electricity will be returned..._

ABrass

DiggerUK said:

The array the OP is considering to have installed is 8.9 KW, which would require 27(?) x 320 W panels. The are claimed to have a 20% efficiency.  If the OP is expecting the plated 8.9KW to be produced they could be in for a disappointment, especially as degradation of solar panels is a given known over time and will reduce the power output.
They don't appear to have any producers warranty/guarantee so they will need to carefully check the suppliers warranty/guarantee insurance and who it is with.

The same due diligence for who is responsible for the warranty/guarantee on the inverter needs to be clarified 

The costs for insurance on such installations is fairly bog standard. This site I found representative.

All in all I don't see much due diligence from the OP with regards to the  downsides of this project. MSE is after all a money saving site and this project looks overpriced for what electricity will be returned..._

You don't know much about solar panels do you? Or reading.

The OP has already factored in panel degredation, it was there in the beginning. You seem to be getting confused between the efficiency of a panel (how much of the energy that hits it compared to how much is turned into electricity [roughly 20%]) and the panels performance compare to the rated value (typically 100%+ when new [panels are often underrated as it's cheaper to over deliver than get something exactly on 320W], dropping to 90% over 25 years). JA only give a 25 year warranty of 80%-83% but  unusually that degredation has already been factored in in the OP. You keep pretending it's not there, but it is.


You've also ignored the availability of cheap manufacturers warranties and the money saving advice that extended warranties are normally a rip off.

Get back under your bridge.

Martyn1981

DiggerUK said:

The array the OP is considering to have installed is 8.9 KW, which would require 27(?) x 320 W panels. The are claimed to have a 20% efficiency.  If the OP is expecting the plated 8.9KW to be produced they could be in for a disappointment, especially as degradation of solar panels is a given known over time and will reduce the power output.
They don't appear to have any producers warranty/guarantee so they will need to carefully check the suppliers warranty/guarantee insurance and who it is with.

The same due diligence for who is responsible for the warranty/guarantee on the inverter needs to be clarified 

The costs for insurance on such installations is fairly bog standard. This site I found representative.

All in all I don't see much due diligence from the OP with regards to the  downsides of this project. MSE is after all a money saving site and this project looks overpriced for what electricity will be returned..._

I don't think you understand any of this.
The 8.9kWp rating is at 20% efficiency for those panels. In fact the kWp rating for any install takes into account the relative efficiency of the panels chosen.
The OP will see that figure when the panels are cool, particularly April/Oct when they may see 100%+ briefly.
The average output of the panels is taken into account in the annual average, which appears to be conservative, unless the install is E, W or E/W, or shaded and far north.
In this instance, and based on the OP, I'd say frozen_wastes is doing very well on the 'due diligence' front, absorbing the right information and asking the right questions.

People who are particularly anti-PV or anti-RE giving poor advice on here is not new, it's gone on for a decade, typically highlighted by comments about efficiency, degradation and maintenance costs, all of which flies in the face of reality, and the experience of actual PV'ers.

Exiled_Tyke

This looks good. But I have a few comments. 

1. I'd always get more than one quote. 
2. The inverter appears massively over-spec to me. Martyn is probably best to advise on this though. 
3. Aren't in-roof installations less productive than on-roof, as they get hotter? 
4. I presume being such a large set-up that your have different orientations and possible shading thus necessitating the SE system?  

frozen_wastes

Exiled_Tyke said:

This looks good. But I have a few comments. 
3. Aren't in-roof installations less productive than on-roof, as they get hotter? 
4. I presume being such a large set-up that your have different orientations and possible shading thus necessitating the SE system?  

3.  Yes, my objective for in-roof system is purely aesthetic.  But..... there is a silver lining.
https://www.gseintegration.com/Docs/Intl/EN/PS_BOOK_EN.pdf
You can duct that hot air into your house, or dump it to atmosphere.  I'm not speccing this system today, but it's an intruiging possibility that could help in the fringe months with daytime heating of the building.

4.  There is partial shading from both a chimney stack (a thin one), and some trees.

1. I'd always get more than one quote. 

I made four request for quotations maybe 3-4 weeks ago to four companies.  This is the first returned quote.  I'm expecting one more "ballpark" estimate from another, but they have said that in roof systems were more expensive, so I'm not having high hopes.

The other two companies were a little too cynical about my desires to have a large system, and one of them wasn't even MCS registered (they were previously, but thought it a waste of money).  A conversation with them suggested that their thinking was rather "old school" in relation to solar systems, and they told me that a lack of MCS subscription for me did not translate into a cheaper price for my system.

So that's all my local options exhausted.  I'm reluctant to go with a National Installer, as I think that they are far more likely to "cheap out" on various components and construction methods.

Martyn1981

Exiled_Tyke said:

This looks good. But I have a few comments. 

1. I'd always get more than one quote. 
2. The inverter appears massively over-spec to me. Martyn is probably best to advise on this though. 
3. Aren't in-roof installations less productive than on-roof, as they get hotter? 
4. I presume being such a large set-up that your have different orientations and possible shading thus necessitating the SE system?  

Hiya ET, I bottled it! I thought should I mention inverter sizes and confuse the issue, or keep my big gob shut?
But yes, I think the 10kW model is way oversized and can cope with up to 15.5kW DC whereas the 8kW model seems ideal as it is ~10% undersized (ideal for the UK to maximise annual generation), but can still cope with 12.4kW DC.

@ frozen_waters - The 10kW model will cost a bit more, and probably underperform during low generation periods (which the UK specialises in) giving you less annual generation than a smaller model. Once the panels are hot, which will happen in direct sunlight, they will drop to 90% output very quickly, and run at around 80% during the summer unless the air temps are particularly cold. So the system will spend very little time generating over 8kW AC, but a lot of time generating low levels in poor weather, low sun angle and mornings/evenings.

Coastalwatch

Hi FW,  Having an almost Identical system to the one you're proposing I can only concur with your thoughts on consumption and for planning ahead so far. We've an 8.85 kWp array facing SSE with a 23 degree pitch forecast to produce 9060 kWh's annually. The Solar Edge system with HD wave inverter(warranty ext to 25yrs) is great for checking on output, not only in total but for individual panel output too, so it's easy to detect if there's a fault and identify it's location as well.

It's been in for two years now during which time we've added an EV, replaced GCH with two ASHP's, installed a thermal storage tank and replaced the gas hob with an induction version. So now totally dependent upon electricity apart from our rarely used Renault Trafic.

As far as I've been able to ascertain Output from the array is similar to our annual domestic consumption, plus also covers 5k miles of motoring.

The cost of our installation was similar to that you've been quoted and we don't regret it. The ROI might be 15 - 20 years and we may not be here to collect upon it, but our children or G'children will.

Enjoy the journey you've embarked upon, we are still. Couldn't have done it without the help of the guys on here who are very knowledgeable. Naturally you get the odd one who isn't but suspect you'll be able to sort the wheat from the chaff without too much anguish.

frozen_wastes

Coastalwatch said:

Hi FW,  Having an almost Identical system to the one you're proposing I can only concur with your thoughts on consumption and for planning ahead so far. We've an 8.85 kWp array facing SSE with a 23 degree pitch forecast to produce 9060 kWh's annually. 

Very interesting to note.  Out of interest what part of the country do you live in, and how much shading are you contending with?
I'm up in Aberdeenshire, so I'm expecting solar insolation over the course of the year to be maybe 20% lower than examples in the south of england.

frozen_wastes

Martyn1981 said:
The 10kW model will cost a bit more, and probably underperform during low generation periods (which the UK specialises in) giving you less annual generation than a smaller model. 

Out of interest, why would a higher max rated inverter perform worse at low outputs?

Actually,  that may not be the right question.  Better question:  Is there a graph that shows an input/output curve for the different inverters, so I can figure out the conversion efficiency?  I see on the datasheet there's two efficiency ratings: Max Efficiency (99.2%), European Weighted Efficiency (99%).

Hang on,  here we are:
https://www.solaredge.com/sites/default/files/application_note_solaredge_inverters_efficiency.pdf

OK, so let's compare the 8kw vs 10kw at a given output of say 500 Watts & 1000 Watts, Page 11-13...... errr oh dear - they only go upto 6KW for the single phase inverters, and then it's three phase from then on.

OK so lets compare the 4KW with the 6KW inverter, Page 5 & 8
4KW
Minimum Output:  200 Watts @ 94%
Efficiency @ 500 Watts: 97.5%
Efficiency @ 1000 Watts: 98.8%

6KW
Minimum Output:  300 Watts @ 96.75%
Efficiency @ 500 Watts: 98%
Efficiency @ 1000 Watts: 98.75%

Not much in it, but that minimum output is noteworthy, so I had a look at the 2200H model and indeed the minimum output there is about 130Watts.

So, interesting observations.  Very low output certainly matters, so I'll phone up SolarEdge and get some clarifications on these sheets.

..... and here's a technical note on oversizing of DC power supply:
https://www.solaredge.com/sites/default/files/inverter_dc_oversizing_guide.pdf

Martyn1981

frozen_wastes said:

Martyn1981 said:
The 10kW model will cost a bit more, and probably underperform during low generation periods (which the UK specialises in) giving you less annual generation than a smaller model. 

Out of interest, why would a higher max rated inverter perform worse at low outputs?

Actually,  that may not be the right question.  Better question:  Is there a graph that shows an input/output curve for the different inverters, so I can figure out the conversion efficiency?  I see on the datasheet there's two efficiency ratings: Max Efficiency (99.2%), European Weighted Efficiency (99%).

Hang on,  here we are:
https://www.solaredge.com/sites/default/files/application_note_solaredge_inverters_efficiency.pdf

OK, so let's compare the 8kw vs 10kw at a given output of say 500 Watts & 1000 Watts, Page 11-13...... errr oh dear - they only go upto 6KW for the single phase inverters, and then it's three phase from then on.

OK so lets compare the 4KW with the 6KW inverter, Page 5 & 8
4KW
Minimum Output:  200 Watts @ 94%
Efficiency @ 500 Watts: 97.5%
Efficiency @ 1000 Watts: 98.8%

6KW
Minimum Output:  300 Watts @ 96.75%
Efficiency @ 500 Watts: 98%
Efficiency @ 1000 Watts: 98.75%

Not much in it, but that minimum output is noteworthy, so I had a look at the 2200H model and indeed the minimum output there is about 130Watts.

So, interesting observations.  Very low output certainly matters, so I'll phone up SolarEdge and get some clarifications on these sheets.

..... and here's a technical note on oversizing of DC power supply:
https://www.solaredge.com/sites/default/files/inverter_dc_oversizing_guide.pdf

Hiya. I think the links kinda say it, but perhaps think of car and engine choice. If you are going to mostly drive at 30mph then a small efficient engine makes sense, but if you plan to drive at 100mph most f the time, then the small engine will be working its socks off and suffering, whereas a larger engine will cope far better.
So for instance in Spain, you expect good strong sun, most of the time, and install an inverter that can take the strain, and may be a bit inefficient (big) at low levels, but this can be ignored. But in the UK you don't expect max gen very often, so a small amount of capping is acceptable in order to boost efficiency at low and lower levels of generation.
There's no one size fits all, so south facing on the Cornish coast with lots of sea breeze cooling, you might go for 0-10% undersizing, but an E/W install, in-land in the North of England might be 10-20%.
Plus of course you have to look at the inverter sizes available, as that might dictate the decision somewhat. In your case an 8kW seems to hit the sweetspot on the nose, whilst the 10kW is very big. Thankfully there isn't a 7kW nor 9kW to make our heads hurt with over consideration.