# Solar Electricity generation



## 9fingers (31 Oct 2010)

Is anyone here considering or already have, a UK domestic solar electricity micro generation scheme installed and interesting in comparing notes please?

Cheers

Bob


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## dickm (31 Oct 2010)

Now who'd have thought Bob would be considering that?????

I had my panels installed at the beginning of October, and they're generating away happily, even with our short days and low sun.


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## miles_hot (1 Nov 2010)

Bob

See this thread for plenty of information on PV etc.

Im still not 100% clear on the investment though - it still feels like a long term investment with a significant number of years until you've broken even.

Miles


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## misterfish (1 Nov 2010)

Yes. If you look at the other thread (mentioned above) that I started last year there are some basics of our system. As somewhat of a geek I have been keeping daily stats of our system including the installation of a datalogger that records data every 5 minutes.

Our first 3 months of generation finishes next weekend and we have to submit our first reading for the Fedd In Tariff payments and I'll extrapolate from that the realistic potential. 

Let me know what info you're interested in. Of course, you're welcome to come and look at our system

Misterfish


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## 9fingers (1 Nov 2010)

misterfish":3qdfb3f5 said:


> Yes. If you look at the other thread (mentioned above) that I started last year there are some basics of our system. As somewhat of a geek I have been keeping daily stats of our system including the installation of a datalogger that records data every 5 minutes.
> 
> Our first 3 months of generation finishes next weekend and we have to submit our first reading for the Fedd In Tariff payments and I'll extrapolate from that the realistic potential.
> 
> ...



Jeff, I don't know how I missed your earlier thread. I must have been spending too much time on other forums :lol: 

I too will want to be monitoring my system which will be on my workshop roof. One of the companies who are quoting have been asked to look at inverters with ethernet interfaces to run the data back to the house.

I particularly what an inverter from a company that will support data collection and provide suitable software etc as well as give good tech support to a technical customer.

I'm still in the infancy of my collection of info about these systems and am sure to be back in contact when I can formulate focussed questions.

In the meantime - who did you get to do your installation and would you recommend them to others?

Cheers

Bob


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## misterfish (1 Nov 2010)

Hi Bob

We went with Southern Solar and have been impressed with their thoroughness and professionalism throughout.

We have a Fronius IG30 inverter - which allows the connection of multiple strings of PV panels. In our case we have three strings of 5 panels at different angles of inclination - one string on the main roof of the house and two on the flat roof of the sun room/granny annex.

We have a personal display (wireless) attached to our system that gives a remote display of the inverter data and also a usb attached datalogger that connects to the desktop PC. I did look at a more sophistcated version of the datalogger that would attach directly to our network switch and allow monitoring from any of our PCs, but it was silly money (over £1000).

Jeff


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## dickm (1 Nov 2010)

(already PMed this to Bob, but just for the record)
Our system uses an Aurora inverter. Basically, I took what the installers (E-motion Energy, with a base in Stirling) suggested, but reading the instructions, it has at least a USB connection and I have a disk with the software for working with it. But can't be a**sed to do the necessary connection. Probably should do something, so as to get warning of any problems, but at the moment just reading the generation meter and multiplying by 41p keeps me happy! 
Hard to tell what the payback period will be, as we are now in the long dark nights of the Scottish soul, but making some optimistic guesses, it's not unreasonable.


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## Carlow52 (1 Nov 2010)

As a matter of interest what life span are the different suppliers quoting for the PV panels?

Thanks


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## 9fingers (1 Nov 2010)

Carlow52":22vpntzd said:


> As a matter of interest what life span are the different suppliers quoting for the PV panels?
> 
> Thanks



Most of the manufacturers seem to be standardising on quoting better than 80% of rated performance after 25 years.

Bob


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## 9fingers (19 Nov 2010)

After numerous quotes and differing degrees of BS from reptiles, I have now put down a deposit for a Solar PV system for my workshop roof.
It should be installed in January as I have chosen a panel size made from unobtainium in UK but will get a better yield from my particular roof area/aspect ratio.
Predicted return is abut 11% per annum on capital invested so will better than the building society!
It certainly pays to shop around as some systems would generate more power but the extra cost reduced the yield to 9%!

Thanks for everyone's input.

Bob


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## Dibs-h (19 Nov 2010)

9fingers":1d9qzfa6 said:


> After numerous quotes and differing degrees of BS from reptiles, I have now put down a deposit for a Solar PV system for my workshop roof.
> It should be installed in January as I have chosen a panel size made from unobtainium in UK but will get a better yield from my particular roof area/aspect ratio.
> Predicted return is abut 11% per annum on capital invested so will better than the building society!
> It certainly pays to shop around as some systems would generate more power but the extra cost reduced the yield to 9%!
> ...



My shed roof (well the front anyway) is the only true south facing roof we have. The main house one is E-W. 

Although 2 dormers (about 8m2 each) have flat roofs, so could stick something on there. I too, am wondering about fitting solar panels to it, but up till now it was really with Thermal Solar (tubes) in mind. The cost is far less and we use a damn sight more gas for heating and DHW than 'lecy.

But this thread has got me thinking tho. Spill the beans Bob. :lol: What sort of panel, size, output, cost, etc.?

Cheers

Dibs


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## 9fingers (19 Nov 2010)

Dibs,

You don't really make any significant saving on the cost of the leccy generated. The real gain is from the (crazy) feed in tariff as they call it.

The system is fitted with a meter that measures how much you generate
For very kWhr your system generates, you are paid 41.3 pence
As your current house power cant identify what you send back to the gird,
they assume that 50% is sent back and you use the rest.
BUT they cannot check this and you can use it all yourself!

For every kWhr assumed sent back you get 3p - this is the same as getting 1.5p for every kWhr you generate.

For every kWhr that you can use from what is generated, you don't have to pay for. saving maybe 13p per unit.

If you modify your domestic consumption pattern to use all the power you generate (without wasting it) you power bill should be reduced by 13p per unit.

So you definitely get 42.8p per kWhr and with care, upto 55.8p per kWhr


My system uses 10 x 235watt panels. These don't genarate the maximum all the time naturally but factoring in the location, annual variations in light levels etc, the output is estimated to be 1860kWhrs per annum.
With care, I should benefit by £1000 per annum. The crazy thing is buying that amount of power from the grid would be about £240!!

The tariff is index linked and guaranteed to be operative for 25 years

Maintenance should be no more than power washing the glass once a year.
The inverter that generates the mains power from the panels cost about £1200 and is warranted for 5years but the technology is mature.

The cost of my system will be about £8500 inc 5% vat for the hardware, installation and scaffolding to single storey roof.
The panels are 1652 x 994 x 46mm covering about 16.5 sq metres.

If you have more questions then feel free to ask.

Bob


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## dickm (19 Nov 2010)

Sounds like you got a pretty good deal there, Bob. My 3.9kW system (17 panels) cost something under £14k, including labour for fitting.

As you say, the feed in tariff is crazy, but if it's there for the taking, tax free, and if you can raise the cash, then seems mad not to go for it. It will be paying you something over 8% at worst, which you can't match that easily anywhere else.

Now, what is interesting is the Energy return on investment, that is, the amount of energy generated per unit of energy used in making the panels. An eminent friend insisted that it would take 80 years to regain the energy used, but most other people I've spoken to insist that's nonsense. The latest Dutch data I can find suggest an energy pay back ranging from under a year in Southern Spain (guess why!) up to 4 or maybe 5 years up here in gloomy Aberdeen.
Of course, the fact that the eminent friend has a vested interest in the nuclear industry may colour the figures


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## 9fingers (19 Nov 2010)

You are quite correct, the total energy equation does not make sense and a panel will not generate anything like the energy that it takes to make it.

Fitting panels is not a green thing to do. fullstop. no question!

The feed in tariff is there to encourage joe public to fit generation systems that will help meet the commitment make by governments at international tree hugging conferences. If they don't achieve the agreed renewable energy levels then huge fines will be levied on them. It is calculated that paying the tariff will cost less than the fines.

For anyone considering these systems, the current tariff started in April 2010 and will be revised (possibly downwards) in 2013 or earlier if the take up exceeds the expected levels. 
The bandwagon is rolling - jump on sooner rather than later.

Bob


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## miles_hot (24 Nov 2010)

Bob

Who do you go to for your pannels?

I'm always confused by the "return on investment" idea; maybe you can throw so light into the darkness of my ignorance? 

If you've spent £8500 on the system and you are clearing £1000 / year that seems to mean that you will break even in 8 years, 6 months. Until that point the "investment" isn't making you any money. Am I missing something here as every one talks about this being better than money in the bank etc but until you've broken even that's not the case (assuming that the capital value of the system is zero which could be unfair).

Now, assuming that the above is right (which is a big assumption I'll grant) I modelled the effect of putting £8.5K in the bank vs on the roof and found it would take 27 years for the PV to out perform the bank:

PV:
Year Return Balance
0 0 -8500
1 1000 -7500
2 1000 -6500
...
10 1000 1500
11 1000 2500
....
26 1000 17500
27 1000 18500

Bank (2.9% interest rate - best rate from Google today)
Year Return Balance
0 0 8500
1 246.50 8476.60
2 253.65 9000.15
....
10 318.33 11312.87 
11 328.07 11640.94
...
26 503.73 17873.87
27 518.34 18392.22

now all this of course assums not only a daft level of interest rates but also that energy costs will not rise inflating the rate of return etc (or would that depress the rate of return as the energy costs start to climb towards the artificial feed in rates?)...

Can someone point out to me which end of the stick I'm holding as I still can't see that PV makes sense and I really would like to be able to do it!

many thanks

Miles


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## Dibs-h (24 Nov 2010)

miles_hot":u545nezx said:


> Bob
> 
> Who do you go to for your pannels?
> 
> ...



I'm kind of with you on this. References to a return of x%, better in the bank makes the assumption that you can "liquidate" your investment and retrieve your X thousands. Which as it has to be fitted by an "approved" installer - I would suspect a large portion of X thousands is labour. The second hand value would be significantly less than what was paid for it. Selling the house isn't really an option for most folk - as the ones who bought them yrs and yrs ago would have sold to realise the capital gains - but didn't (probably due to being happy where they were, or good schools, family nearby, etc.)

In which case it isn't a return - you've effectively lent someone your money and they'll give it back to you at a very slow rate.

I think I'm more inclined to stick with Plan A - fit Thermal Solar and knock off a sizeable amount off our gas costs. We are upgrading the plumbing ( due to it probably be older than me), etc. anyway so the additional costs are marginal, but the savings aren't.

Dibs


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## 9fingers (24 Nov 2010)

Miles, 

The panels are made by Sharp but there are many suppliers using semiconductors from about 6 worldwide suppliers.

Your figures have not included the promise that the feed it tariff is index linked (to one of the standard inflation measures - Possibly CPI)

Roughly 75% of the annual 'earnings' of the system comes from FIT rising with inflation, and the balance from electricity costs saved which will arguably rise at greater than inflation.

This makes modelling quite complex.

Picking a couple of figures from the air
Inflation =2.5% and electricity increase over and above inflation 3%
make the return exceed your bank investment figure in year 19.
juggling these figures can take this forward to year 15 with ease.

I don't know if your bank interest figure is gross or net of tax but any further investment income would put me in the 40% tax bracket. That is my problem but a true comparison needs to bear in mind your marginal rate of tax. Anything gained from PV is tax free.

I have not considered any increase in capital value of my house as a result of this installation but the sales pitch figures claim 5-10%.
I have decided that I will leave this house in a box (or in a state of mental decline that means I don't care) and that other medical disasters excepted, that should be in at least 20 years maybe more.

I did look at solar water heating and rejected it on the grounds of 
1) much lower payback rates on capital employed (A friend has spent £4000 and is saving £200 pa and will be fortunate to live another 10 years))
2) The system would have to be on my house roof and that is shaded by next door whereas the PV system can go on my workshop roof which is not shaded.


Dibs - The labour element of the installation is £900 +5% vat 
However it would be prudent to assume only scrap value for the who installation at the end of the FIT period of 25 years.

cheers

Bob


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## RogerS (24 Nov 2010)

Bob

What are the practical aspects of installation from the cabling point of view? Distance from panels to meter, capacity etc.

Roger


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## Dibs-h (24 Nov 2010)

9fingers":3d9277em said:


> I did look at solar water heating and rejected it on the grounds of
> 1) much lower payback rates on capital employed (A friend has spent £4000 and is saving £200 pa and will be fortunate to live another 10 years))
> 2) The system would have to be on my house roof and that is shaded by next door whereas the PV system can go on my workshop roof which is not shaded.
> 
> Bob



In our case the Solar Option can't really go on the house as it's E-W facing whereas the shed roof is S facing and slightly closer to where the "tank" will live as opposed to roof (3 stories up).

I'll have to dig out the spready again and see what the savings are likely to be. The marginal cost for us to go solar would be <£2k and the potential savings far more than £200 (probably double) so for us.

Cheers

Dibs


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## 9fingers (24 Nov 2010)

RogerS":2lshcrbp said:


> Bob
> 
> What are the practical aspects of installation from the cabling point of view? Distance from panels to meter, capacity etc.
> 
> Roger



Cable runs are not an issue as the system can connect in anywhere that you have enough cable capacity. I have 2 x 4mm cables into the workshop.
System output will be about 2kw peak so even 1.5mm cable would be enough although they recommend 2.5.
The inverter connects to its own (export) meter which you own - not involved with your leccy board (import) meter at all.

My panels will be 30m or more from my import meter and main CU

HTH

Bob


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## dickm (24 Nov 2010)

RogerS":1tt90dcb said:


> What are the practical aspects of installation from the cabling point of view? Distance from panels to meter, capacity etc.



Not sure about the total distance that is acceptable, but my guess is that only the distance from panels to inverter is critical, because it's lower voltage/higher current. Our inverter is in the loft, about 3 feet below the panels, and that seems to be the preferred arrangement. Then from there down to the meter (by the consumer unit, but I guess it can be anywhere convenient) it's standard 240V 2.5mm2 cable. So could probably be quite a long length. (I assume you mean current capacity?)
Our panels are Moser Baer, which despite the germanic sounding name are actually Indian. 
Labour was less than 5% of the cost of the installation - the hardware is the expensive bit. 
We used a local-ish installer, E-motion Energy, based in Stirling, but they have branches in Birmingham and Belfast and possibly elsewhere. I'd recommend anyone interested at least to try them, as they seemed to be keen and were not out of line on cost. 
It's interesting that we are now getting a steady stream of offers to install Solar PV from others getting in on the act.
Like Bob, I'm assuming/hoping the system will outlive me, so the residual value is of academic interest only.


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## 9fingers (24 Nov 2010)

Dibs-h":1e0ga8k9 said:


> 9fingers":1e0ga8k9 said:
> 
> 
> > I did look at solar water heating and rejected it on the grounds of
> ...



I think my pal paid too much for his system but he is not a diyer or aware of what things would cost. he did get a dirty great thermal store installed in the loft as well as the panels

There is only him and his wife and he admits he can't use all the hot water that a 20 tubes system produces.
A family with kids would use a lot more DHW so I agree the payback will likely be much better for you.
Also i think you are allowed to install some of it yourself for further saving.

PV systems must be installed my register installers in order to qualify for the FIT and the 5% vat rate.

Bob


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## 9fingers (24 Nov 2010)

dickm":3c37qcop said:


> RogerS":3c37qcop said:
> 
> 
> > What are the practical aspects of installation from the cabling point of view? Distance from panels to meter, capacity etc.
> ...




DC voltage from a string of panels is in the range 200 -700 volts depending on no of panels and light levels.

Inverters tend to be most efficient in the 400-600 volt range.
Installation manuals tend to suggest max voltage drop of 1 volt at maximum smoke and indicate 4mm cables for my 2kw system. My max panel current is spec'd at 8 amps.

Bob


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## RogerS (24 Nov 2010)

Thanks, Bob.


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## 9fingers (3 Feb 2011)

Well it has finally happened. The Solar electricity system is now installed.

A clear southfacing roof 







now looks like this






And some clear wall space 






Now looks much more impressive!





Since installation the weather has been pretty dull and although the system is generating some power, it is nowhere near it's full potential. I'm collecting data and once I've got a reasonable amount I can post some charts.

So far so good!

Bob


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## RogerS (3 Feb 2011)

I've always been a bit bemused how you can 'push' your volts into the grid. Surely you have to be 0.00001v higher in potential than the grid? But then if your neighbour is also 0.00001v higher, you'd need to be 0.000011v higher but then he'd not work..... :?


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## 9fingers (3 Feb 2011)

The inverter monitors the grid voltage and phase and manages the infeed automatically by trying to generate at a slightly higher voltage than the local sample of the grid
In practise, it pays to arrange to consume the power (usefully, of course) yourself rather than let the grid have it.

The finances are crazy.
You get 43.5p per kwhr generated.
You get a further 3p per unit exported. However they cannot measure how much you feed into the grid so they assume 50% and also don't mind if you consume it all yourself.
So bottom line is you get 45p per unit and can potentially save the same number of units off your normal bill ie another 10-11p per unit.

I told you it was crazy! Must have been designed by a politician!!

Bob


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## bugbear (4 Feb 2011)

miles_hot":3eupxez3 said:


> Im still not 100% clear on the investment though - it still feels like a long term investment with a significant number of years until you've broken even.



Surely that's what you'd expect?

BugBear


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## bugbear (4 Feb 2011)

RogerS":12qgrznq said:


> I've always been a bit bemused how you can 'push' your volts into the grid. Surely you have to be 0.00001v higher in potential than the grid? But then if your neighbour is also 0.00001v higher, you'd need to be 0.000011v higher but then he'd not work..... :?



The same logic applies if there's more than one power station ... in the UK !

I think we can safely assume "they" have found a solution...

BugBear


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## RogerS (4 Feb 2011)

bugbear":20hfi3i9 said:


> RogerS":20hfi3i9 said:
> 
> 
> > I've always been a bit bemused how you can 'push' your volts into the grid. Surely you have to be 0.00001v higher in potential than the grid? But then if your neighbour is also 0.00001v higher, you'd need to be 0.000011v higher but then he'd not work..... :?
> ...



I know..but I wish I knew how. Can't see how Bob's inverter 'wins' over everybody else's inverter.

Interested also to learn more about the cost benefit equation/payback period.


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## 9fingers (4 Feb 2011)

As far as costs and payback are concerned, I only have estimates.
The system cost £8600 and is predicted to 'earn' £900 to £1000 in a year and the FIT is indexed to RPI, and the electricity cost saving is linked to energy prices obviously.
Ironically I have just reduced the latter by changing to what I hope will be a cheaper supplier yesterday!

Bob


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## RogerS (4 Feb 2011)

So is that 'income = £900-£1000' a year PLUS saving on the electricity bill?

If so have you done any calc, Bob, on what % of electricity you might save ?


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## 9fingers (4 Feb 2011)

No, that figure includes the estimated saving on the leccy bill. To maximise the saving I need to find ways of gearing my consumption to the peak generation pattern of the PV system. Ways to do this are not yet obvious but I'm thinking about it!

Whatever happens, I will still get the 45p per unit, managing to maximise the further 11p per unit is the challenge. Things like charging batteries to run the lighting at night does not make sense due to further capital outlay needed. I need to be in the workshop sawing up lots of wood in the middle of summer days I guess!

Bob


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## bugbear (4 Feb 2011)

RogerS":25um2sid said:


> Interested also to learn more about the cost benefit equation/payback period.



If George Monbiot's number's are right, it's currently a bonanza if you can afford the capital outlay;

http://www.guardian.co.uk/commentisfree ... NTCMP=SRCH

BugBear


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## 9fingers (4 Feb 2011)

bugbear":ozhn3efw said:


> RogerS":ozhn3efw said:
> 
> 
> > Interested also to learn more about the cost benefit equation/payback period.
> ...



I don't disagree with the points made in the article at all. 
I looked at the scheme with some disbelief in the beginning but when I saw that companies are establishing themselves to put up the finance and reap the FIT for themselves whilst giving the householder the right to any electricity generated, I dug deeper.

I am relatively recently retired and lucky to have a lump sum from my pension. However with (real) inflation at 5 or 6%minimum and poor rates of return from the bankers (silent W) I am slowly losing buying power that I might well need in later life. It seems a no-brainer to invest some of my lump sum in an asset that can earn me some real return.

For anyone thinking of doing the same, do it sooner rather than later. The value of the FIT for NEW sign ups will start reducing by 7% per annum from either April 2012 or sooner if the take up is greater than predicted by the 'plan'.
Once you have locked into a scheme, that installation (who ever owns it) will get payments indexed by RPI (upwards as things are at the moment) whereas FIT for new schemes will reduce.

Bob


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## Eric The Viking (4 Feb 2011)

RogerS":22vag781 said:


> Can't see how Bob's inverter 'wins' over everybody else's inverter.
> 
> Interested also to learn more about the cost benefit equation/payback period.



I'm grossly simplifying, but consider that most mechanical electrical generators can operate as motors too. 

Mechanical force is converted into electricity, but if you take that force away, the generator becomes a motor instead, and rotates in the other direction. The point at which the nett energy transfer is zero will be a certain RPM for each genny. Go slower and it's a load, go faster and it's a generatior.

I'm not considering AC frequency, 3-phase etc. above, as it gets a lot more "interesting" than that, but that is sort-of how it works. 

There was an incident around 1978 or 1979, when the then CEGB got it wrong in the middle of a hard winter's evening and brought up a power station accidentally out-of-phase with the rest of the grid. Immediately the breakers closed it became a load (the generators ran as motors), and they couldn't re-open the breakers as the current surge welded them shut. It blacked out a large part of East Anglia (I was in Lowestoft that night and remember it well), and the station concerned was badly damaged.

Cheers,

E.


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## slimshady (4 Feb 2011)

I wonder if I can put in a small'ish number of panels before the FITs change and then increase the panel count in later years.?

Alex.


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## 9fingers (4 Feb 2011)

slimshady":2ifdloz5 said:


> I wonder if I can put in a small'ish number of panels before the FITs change and then increase the panel count in later years.?
> 
> Alex.



I don't think this will work. The installation has to be done by an accredited installer who registers your system online and they issue a certificate that describes your system.
Additionally, you have to describe your system on the FIT application form including the power output.
Nice try!

Bob


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## dickm (4 Feb 2011)

9fingers":14orfacy said:


> bugbear":14orfacy said:
> 
> 
> > I looked at the scheme with some disbelief in the beginning but when I saw that companies are establishing themselves to put up the finance and reap the FIT for themselves whilst giving the householder the right to any electricity generated, I dug deeper.
> ...


Exactly the same for me, Bob. If you can tie up the cash for a few years, you should be in profit after that, and getting a useful income before. 
Best if you live in the south, and have a south facing roof with a pitch of at least 45degrees. Not as good up here if you have a low pitch roof. We need a steeper pitch anyway (latitude plus 5 deg is recommended) so we don't get as much light per unit area, and the snow lies on the panels because of the low angle. Did wonder before last night whether we should think of getting our panels moved so they are mounted more steeply on frames on the roof, but thought better of it as the gales blew in!
Still waiting for our first payment from SSE, though.


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## 9fingers (17 Feb 2011)

I now have generation data on line for anyone to look at and play with in excel or whatever takes your fancy.
The following is the readme file which include the ftp link and an outline of the system.
Have fun. if you get asked for a username or password then leave blank and hit return

Bob

The files in the directory SBEAM hold power generation data for my solar panel system.

The system comprises 10 x 235w Sharp solar Panels and a Sunnyboy SB2500-30-HF inverter feeding the grid.
The panel area is 16.5 square metres and faces due south at an elevation of 30 degrees.
The location is 50.98723 North, -1.47665 West in the UK.

A SunnyBeam Bluetooth logger captures a generation file around midnight GMT for the preceding day.
In addition, the total power generated that day is added to a monthly cumulative file. Each month an 
additional monthly cumulative file is created and the daily detail data files are removed.
Files are in read only CSV (comma separated Variable) format which can be opened in text editors such as 
notepad or spreadsheets such as MS Excel and Open Office Calc.

Daily file names are in the format yy-mm-dd.CSV and monthly file names are yyyy-mm.csv

To access the data, point your browser to ftp://86.16.36.255

I can be contacted at [email protected]


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## NikNak (14 Nov 2012)

Bob....


Your last posting on this subject seemed to be around 18 months ago.... any update, news, etc you'd care to share with us..? I've tried your 'link' but it doesn't seem to work...  

We too are doing our 'bit' to be green, new condensing boiler, loft and wall insulation, low energy bulbs, 7 (yes 7) water butts, thick lined curtains, eco f/freezeer, eco washing machine, blah blah blah...... and are now thinking about some PV solar panels as the prices seemed to have dropped enormously over the last year. 

Just had a quote to supply and install 14 x 250w panels i.e. a 3.5kw system, for a smidgen under £5k. The only thing the quote doesn't seem to include is a gadget to tell you how much it is generating _'now'_ so you know its the best time to use all that free 'lecky, so i shall ring em and ask if that's included too.



Nick


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## Dibs-h (14 Nov 2012)

9fingers":va4rhve7 said:


> I'm no longer active on this forum. If you want to contact me try [email protected]


I don't think Bob visits anymore.

HIH

Dibs


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## Harbo (14 Nov 2012)

He's also on holiday.

Rod


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## DrPhill (14 Nov 2012)

I have had solar pv for 18 months. Some points:
(1) Ignore the reduction of consumption term in the cost/benefit analysis. Unless you have heavy leccy use that you can shift to sunny days. Mosy of my leccy is consumed when the sun is not shining.
(2) Investigate an export meter. I wish that I had. We use very little electricity, probably less than half of what we generate, so that we are losing a bit of the feed-in tarriff.
(3) Generation seems to be approximately what was predicted, except that this year has been very wet. We are tracking to 10 year payback.
(4) Calculating payback confuses my poor little brain. I calculate two values: 


*(i) How long before the cash gets payed back assuming no loss of interest and no inflation. This is a simple but misleading measure that just compares quidspent with quidsgot. This figure implies a quicker payback, as payments rise with inflation.
*(ii) Return based on leccy units. I spent 25000 leccy units worth of quids to get the thing installed. Since leccy units are (roughly) inflation linked I calculate how many leccy units I have been payed for. This is the figure that implies a 10 year payback. This may or may not be more accurate than the former.
(5) The income from the roof is ignored by both the taxman and the benefits means-test (not that the latter helps me). That increases its value relative to savings interest which is taxable (unless in an ISA etc).
(6) Move the TV ariel from above the solar panels to avoid a drop in generation due to doppings.......

HTH

Phill


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## dickm (14 Nov 2012)

£5k for an installation of that size sounds VERY good. We paid a lot more for a 3.9kW installation two years ago, but at least we get the 43p feed in. Total generation this year was about 5% down on the first year, but we haven't had a summer! Best generation was actually in May and October - June to September were a washout. Daughter in the next village has a newer installation, using (I think) Sanyo panels which appear to be more efficient than our's - their generation this year was 5% over prediction, so it may be worth checking what spec of panel your installer is offering.
Agree that it's difficult, but it's not impossible, to push more of your consumption on to the panels. If your wiring and appliances are all reliable, it may be worth putting things on timers to run them during the day, even if you are not in the house. 
We decided not to go for an import/export meter as we still probably use more than 50% of generation. 
We are on track for a 10year basic payback too. 
One thing probably worth doing is looking at maintenance contract; it's not clear how long inverters etc. will last, and difficult to know if panel performance is degrading over time. A good installer should cover these things at an annual inspection.


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## Eric The Viking (14 Nov 2012)

The scam, er, scheme has ended. The gravy train (for the installers) is hitting the buffers: it's now a buyer's market.


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## Benchwayze (14 Nov 2012)

As we are discussing Solar Panels:

My house ridge runs directly N/S. So:

Do you HAVE to have the panels on your roof or could they be fitted on the flat garage roof, at 45 deg lean-to against my South facing house wall? 

TIA


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## wobblycogs (14 Nov 2012)

As long as they point at the sun and have a clear view of the sky you can fit them anywhere. We're planning on putting them on a flat roof - once it's been built.


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## Benchwayze (14 Nov 2012)

Thanks Wobbly. 
I take it the best plan is to have them on a driven, equatorial mount then.  

I could put them on the East facing pitch of the roof, with a full 180 degrees of clear sky, but after dinner time, the old Earth has rolled around a bit; whereas, in the summer, and on the South facing gable, they would get Sun for almost all of the day.

Cheers again.


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## dickm (15 Nov 2012)

Oddly enough, just noticed that a house in the next village with a ridge running north-south has just had eight panels fitted on one side and eight on the other. It would need either two inverters, or one that will accept more than one array, but is probably quite an efficient arrangement. 
A friend down in Yorkshire who has a reasonable amount of land has had his panels ground mounted, which works really well because you can optimise the angle to the horizontal. But he hasn't (yet ) installed a rotator as well.


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## Benchwayze (15 Nov 2012)

Thanks Dick. 

On the West-facing pitch there is no view other than next door's roof! That's the side planning would have had me fit a dormer for a loft conversion BTW!

A rotator I presume is a driven, equatorial mount, (as per Astronomical Telescopes.) to counter the Earth's rotation, so as to remain trained on the desired object. In this case, the Sun. I think I'll just lean them against the bathroom wall, beneath the window. !!


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## Robbo3 (16 Nov 2012)

To come in late on this subject..... my 2.1k system is now 14 months old & has given me a cash return of approx £1000 plus lower bills over that period.

I obtained three quotes & asked a number of questions about the system. Below are the answers that I got.
Although I didn't know until he arrived, the installer I chose was a school friend & he confirmed these answers.

East & west facing arrays are approximately 15% less efficient than south facing arrays.
The system accepts input from each panel at the rate of the lowest performing panel, therefore if your panels face a mixture of directions it drags the overall efficiency down. This can be overcome with a second invertor but probably not worth it due to cost.

Replacement costs : Invertor £800, photovoltaic panel £200.

Remember the panels are photovoltaic meaning that they convert light into electricity, Don't get them mixed up with solar heating panels which rely on gaining as much heat as possible.

In our area planning permission is not required for roof mounted systems (excluding listed buildings etc) but planning permission is required for a ground array.

HTH
Robbo


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## misterfish (16 Nov 2012)

Robbo3":oh1fenwu said:


> The system accepts input from each panel at the rate of the lowest performing panel, therefore if your panels face a mixture of directions it drags the overall efficiency down. This can be overcome with a second invertor but probably not worth it due to cost.



We' ve got 15 panels but due to roof shape and size they couldn't all be mounted with identical orientation so they are divided into 3 batches of 5 panels, Rather than having 3 invertors we have a single multistring convertor that allows each group (string) of panels to be processed separately. 

As for actual production - last year we produced 119% of the expected certificated calculated value for our system. This year, despite the poor weather we have produced 111% of what would be expected to date.

The vital requirement fo PV is to ensure that shading is kept to a minimum - in our case early in the morning.

Misterfish


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## gregmcateer (16 Nov 2012)

We've just got 6 x 250w panels due to roof shape. Probably could have squeezed more on if risked wrath of authorities.
Even so, we have cut our leccy cost by nearly 40% over this shockingly poor year AND had back a bit under £400 in FIT (feed-in tariff) payments - So I am pretty happy with them.


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## dickm (16 Nov 2012)

One thing it's worth noting is that councils are _supposed_ to allow PV panels without any problems, unless they are on a listed building. Certainly up here, they are deemed to be "permissible development". The directive from Govt to that effect is one of the few examples of Westminster actually having any interest in green issues.


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## Robbo3 (16 Nov 2012)

misterfish":q2nx8rhb said:


> We' ve got 15 panels but due to roof shape and size they couldn't all be mounted with identical orientation so they are divided into 3 batches of 5 panels, Rather than having 3 invertors we have a single multistring convertor that allows each group (string) of panels to be processed separately.


Interesting. How much more expensive was a multistring convertor?

Our property is 'L' shaped with south & west facing legs of equal length. One company wanted to put panels on both roofs with two invertors, but I wasn't interested & didn't pursue it any further. I wish that perhaps I had now.

Robbo


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## misterfish (17 Nov 2012)

Our system uses a Fronius IG30 inverter - and each of the three strings of panels feeds into it with its own cables. I think the current cost of an IG30 is about £950. Although our panels all face in the same direction (SSW) there are 5 on the main roof and 10 on the flat roof with each of the groups of 5 at a different angle. This layout was only decided after a very thorough survey using a specialist solar meter and software that measured the light levels all over the roof and which took account of all potential shading from chimneys, gables etc as well as other light reflections. The survey took about three hours and assessed the potential generation throughout the year.

Misterfish


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## NikNak (2 Dec 2012)

Well..... we went for it... :shock: 


A 3.5kw (14 panel) system, facing roughly SE'ish (but probably a tinsy bit more to the E), fully installed and g'teed for...... £4600  


Here's a few piccies for you to see....



































would have preferred a 'portrait' layout as they call it, but would only have got 12 panels on. So they suggested this layout for 14 panels, and i must admit it sort of 'suits' the roofline....

The SMA Sunny Boy inverter is mounted in the garage, which is approx 20 - 25 mtrs from the panels, and the mains consumer unit is approx 2.5 mtrs the other side of the garage wall in the little room downstairs.

The green light on the display panel is showing its 'generating', and the blue light is the bluetooth 'activated' light i.e. the comp is downloading the data as seen in the last chart pic (the software is freely available from the SMA website).


We've got one of those 'Owl' thingamys in the kitchen, been there for nearly 3 years now, and shows how much 'lecky we're using etc. funny thing is, its started to do weird things now this is up and running...... as in it goes UP when lecky is being produced, and then down when we turn something on... :shock: (i've searched Owl's website and it seems this is normal, we will need 2 gadgets now if we want to monitor 'realtime' whats being produced and whats being used, without resorting to turn the comp on and use the SMA s/ware).

I know its only been 3 days since install, but must admit so far we have not regretted it and looking forward to the summer...  



Nick


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## dickm (2 Dec 2012)

Can't quite read the scale on your graph - what is the peak generation on that day? And what is the (rough) slope of your roof? Somewhere I've seen it suggested the panels should be at latitude plus 5 degrees. Difficult on a bungalow in Northern Scotland, but probably OK for a house in the sunny south.


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## NikNak (2 Dec 2012)

Hi, 

peak on that day (1st day of generation...) was 1.668kw, total for the day was 4.874kwh

slope.... ummm... 30° ?? ish :? (if i was any good at maths i could work it out... maybe...  )



Nick


oh, meant to say... each of the 3 days so far have started with quite a heavy frost which (although still generating) takes quite a while to clear from the panels.


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## wobblycogs (2 Dec 2012)

I've just done a quick calculation of payback for your system and I'm really surprised how cheap solar power has become. I'm going to ignore the FIT scheme as I wan't to see if solar electricity can compete with normal electricity on a level(ish) playing field. 

Lets say that a unit of electricity is 12.1p/kwh. That means you generated 59p of electricity that day so the payback time would be 7796 days or 21.3 years. I'm guessing that your panels probably have a 25 year guarantee on them so even if your average day is like winter it seems the price is about what regular power generation is costing (ok, this doesn't take into account the drop in performance of the panels or the transformers failing etc etc).

The point really is that solar power now looks to be about the same price as mains electricity even somewhere less than amazingly sunny like the the UK. Electricity prices in the UK are only going to go up so I suppose the payback time be significantly less than the above.


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## RogerM (4 Dec 2012)

We have 17 Sanyo monocrystalline panels giving just a smidgin short of 4kw. Our roof faces 10 deg west of south and there is no shade. In the first year (Oct 2011 to Oct 2012) we generated 4451 kwh which is over 10% more than the official estimate, and which paid us just over £2,000 in FIT and export tariff. Our best month by a country mile was May. June was dire - generating less than March. Our annual usage is around 5,000 kwhs. Assuming average RPI is 3% the system will pay for itself in 6 years making the income for the remaining 19 years of the FIT clear profit, by which time we'll be aged 83. Gives us a good incentive to live that long! Best investment we've made for years.


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## dickm (5 Dec 2012)

RogerM":xlyan0zu said:


> We have 17 Sanyo monocrystalline panels giving just a smidgin short of 4kw. Our roof faces 10 deg west of south and there is no shade. In the first year (Oct 2011 to Oct 2012) we generated 4451 kwh which is over 10% more than the official estimate,


That is b****y good! My system is the same size, but on too shallow a pitch and with some shading and our annual generation at best was 3400kWhr. But that's also Scottish weather for you


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## RogerM (5 Dec 2012)

dickm":2yc489a4 said:


> RogerM":2yc489a4 said:
> 
> 
> > We have 17 Sanyo monocrystalline panels giving just a smidgin short of 4kw. Our roof faces 10 deg west of south and there is no shade. In the first year (Oct 2011 to Oct 2012) we generated 4451 kwh which is over 10% more than the official estimate,
> ...



That's the south Devon microclimate for you.


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## Phil Pascoe (6 Dec 2012)

I think we should have "rain panels" It would make more sense. Rain is fine - except when you have rain before and rain after. You Devon people probably get a bit more sunshine.


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## andersonec (6 Dec 2012)

miles_hot":3bhc4sx2 said:


> Bob
> 
> See this thread for plenty of information on PV etc.
> 
> ...



Miles, I cannot see why the need to calculate a 'break even term' surely the investment you make is to reduce your spending (and all the other benefits) from day one. Does anybody calculate the 'break even point' when they spend £20 grand on a kitchen or £20 grand on a car or £5 grand on a holiday? and can you forecast how much the power companies price rises will be for the next few (and more) years?

The reason companies were bombarding people with phone calls offering free panels was that they were collecting approx ten grand a year from the government for the panels on your roof, 

Fit a ground source heat pump and your total heating and hot water bills will be something like £5/600 a year.

A no brainer to me.

Andy


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## wobblycogs (6 Dec 2012)

This assumes you are lucky enough to have the space for a heat pump of course which most of us don't have.

The difference between a holiday and solar panels is one is done for pleasure and the other as an investment. You'd be crazy not to calculate a break even point and return on an investment. If it takes 10 years to break even you have to either stay in the house for 10 years or be pretty sure that the panels will increase the value of the property (they wouldn't for me) otherwise you are paying to put electricity into the grid.

Solar panels, at the moment, are little more than a savings account on your roof.


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## johnf (6 Dec 2012)

andersonec":1150czks said:


> miles_hot":1150czks said:
> 
> 
> > Bob
> ...



I can confirm that great things heat pumps 24 /7 heating no extra cost


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## andersonec (6 Dec 2012)

wobblycogs":wiqtsqpr said:


> This assumes you are lucky enough to have the space for a heat pump of course which most of us don't have.
> 
> The difference between a holiday and solar panels is one is done for pleasure and the other as an investment. You'd be crazy not to calculate a break even point and return on an investment. If it takes 10 years to break even you have to either stay in the house for 10 years or be pretty sure that the panels will increase the value of the property (they wouldn't for me) otherwise you are paying to put electricity into the grid.
> 
> Solar panels, at the moment, are little more than a savings account on your roof.





Heat pump pipes can be drilled down vertically or there are ones for use in water then again you could fit an Air Source Heat Pump outside your back door, admittedly they are best used on a new build and in conjunction with under-floor heating but these things have been in use in Scandinavian countries for the past forty years or more and should be at the top of any home builders shopping list rather than marble worktops or slate floor tiles and other unnecessary luxuries, I built a garden in Surrey a couple of years ago for the CTO of a very well known mobile phone company, while we doing the job he had the rear of the house rearranged so the view onto the garden was improved, he has since spent one hundred thousand pounds on redoing the kitchen after which they moved???? 
As an aside, while the rear of said house was being rearranged I noticed there was no insulating in the cavity, spoke to the owner who wasn't in the slightest bothered, this was a one million pound house on a gated estate (guarded by ex Gurkahs) built by, you guessed it, Barratts.

You fit such things to cut fuel bills, things such as Insulation and double glazing (what is the break even point on those items?) the rate fuel costs are rising (how long is oil going to last?) you could 'beak even' as you call it in a few short years. 
There is no break even point, you will never get the initial outlay back, it's the same as 'start-up-costs' on any new venture, the outlay is to get the thing set up and in motion, from there on in the rewards of greatly reduced bill are reaped, 

Frankly I think the only way to calculate said 'break even point' is to put the money saved into a savings account (the amount would have to rise as fuel costs rose) and when the savings equaled the initial outlay, voila, you have broke even.

I will say again, if you are producing electricity you will get paid a 'Feed In Tarrif' by your electricity provider, you also get paid for any excess electricity you export into the grid.

Andy


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