Current PV panel prices

keith_r59

tartanterra wrote: »

I meant 300 - 400kg, not 300 - 4000kg; a slip of the finger.
Have now ammended the post.

Point still stands though. You may be surprised to hear that all panels are not a standard weight. Also you can't just glue them onto a roof. They require a mounting system (i.e. steel mounting brackets, coachbolts, aluminium mounting bars etc.).

I'm not surprised to hear that all panels are not a standard weight or that they don't use glue to affix them to your roof.

However, I haven't heard either of any of the tens of thousands of solar pv systems installed thus far causing any roof related problems.

tartanterra

keith_r59 wrote: »

I'm not surprised to hear that all panels are not a standard weight or that they don't use glue to affix them to your roof.

However, I haven't heard either of any of the tens of thousands of solar pv systems installed thus far causing any roof related problems.

And you will find that many of these problems haven't occurred because the installers (or the property owner) has commissioned a survey which is common for any structural change. In the case of new build, the architect takes that responsibility. In the last year we have had only one customer refuse a roof survey and they signed a disclaimer.

zeupater

tartanterra wrote: »

...... You may be surprised to hear that all panels are not a standard weight. Also you can't just glue them onto a roof. They require a mounting system (i.e. steel mounting brackets, coachbolts, aluminium mounting bars etc.).

.... And both the mounting system used and the fixing method is something which many people tend to ignore. Some mounting systems are more aesthetically pleasing than others and some seem to be more secure ...... When looking into systems I was completely surprised by the number of installers who were intending to use what I would consider to be inappropriate fixing systems for my roof ......

I would recommend that anyone looking into pv systems do a little research into the mounting systems and fixing methods being offered against what is available.

HTH
Z

tartanterra

zeupater wrote: »

.... And both the mounting system used and the fixing method is something which many people tend to ignore. Some mounting systems are more aesthetically pleasing than others and some seem to be more secure ...... When looking into systems I was completely surprised by the number of installers who were intending to use what I would consider to be inappropriate fixing systems for my roof ......

I would recommend that anyone looking into pv systems do a little research into the mounting systems and fixing methods being offered against what is available.

HTH
Z

Good advice. It's not just the panels that are important. The type of roof tile you have is a big driver in what type of mounting bracket is used.
You should expect your installer to show you the various types available and explain why they are reccommending a particular type.
Schuco do provide a trade case for installers (at a cost!)to show customers the various fixing systems and mounting rails available.

MASHER154

I have looked into solar panels for the last 3 weeks and had many quotations. It has been very hard deciding between the companies. They all seem to use different panels and inverters. I have narrowed it down now between 2 companies, both with 14 Suntech 280w panels, giving me a 3.92 system. One is using a Sunnyboy 4000TL and the other a Mastervolt 4300. One says its best to keep under the wattage of the panels, whereas the other the opposite. I know that you can be 10% either side, but what is best. Has any body got any views or experience on this.

Thanks

zeupater

MASHER154 wrote: »

I have looked into solar panels for the last 3 weeks and had many quotations. It has been very hard deciding between the companies. They all seem to use different panels and inverters. I have narrowed it down now between 2 companies, both with 14 Suntech 280w panels, giving me a 3.92 system. One is using a Sunnyboy 4000TL and the other a Mastervolt 4300. One says its best to keep under the wattage of the panels, whereas the other the opposite. I know that you can be 10% either side, but what is best. Has any body got any views or experience on this.

Thanks

Hi

The debate on whether to undersize the inverter is a long running one, with many installers sizing the inverter to 80% of the nominal panel kWp .... as an array owner, here's my view ....

The arguement for undersizing inverters is probably based analysis of data collected by the inverters. The data which is recorded is based on the average generation performance of the system over a period of time, in the case of my inverter it's every 5 minutes. Looking at the data you will find that it is very rare to achieve over 80% - 85% of the total installed capacity of the array, this is mainly due to three main factors - firstly, system losses (inverter, cable runs, panel reflection etc) - secondly, temperature (in continuous sunshine the panels heat up and become less efficient) - thirdly, averaging, which seems to be something which is not fully understood by many.

Let me expand on the effect of averaging .....

Panels have a nominal power rating based on an operating temperature which is somewhere around 20C below what their temperature is likely to be after being in full sun for a while which usually reduces the performance by somewhere between 6% & 10% (depending on manufacturer/type). When the panels are cooler than the nominal rated temperature the efficiency increases. Taking this into account you will understand that the maximum performance will be achieved when the panels are cool and the sun shines brightly, which is exactly what you get when you have a blue sky with clouds, or a cloudy sky with blue patches.

As an example, and to keep things simple, let's say that the sky is 50% cloud/50% blue and see what we get. When cloudy let's say the system produces down to 40% of maximum capacity, and when sunny 100% and that there is a regular gradient in the irradiance between the two. This is not untypical.

The average generation of an unrestricted system will be (40+100)/2, so 70% and this is what will be recorded by the inverter for onward analysis, therefore there is an arguement that an inverter rated at 80% of kWp is sufficient in this scenario.

Let's now cap the maximum generation by introducing an inverter rated at 80% of kWp. We have now lost a third of the generation operating band above the baseline 40%, which effectively reduces the total generation in this band by 11.1% (1/9 - simple trig, the top 1/3 of the height of an equilateral or isosceles triangle accounts for 1/9 of the area).

Considering that a loss of 1/9th of 60% of the generation results in an overall loss of 6.7% we suddenly have an alternative position, being that in the conditions as described, an inverter rated at 80% of kWp will result in lost opportunity. This is something which is not apparent when analysing averaged data.

Enough to say, my inverter is sized to utilise the panel performance in conditions such as described in the example above.

HTH
Z

www.mepelectrical.co.uk

zeupater wrote: »

Hi keith_r59

..... I wonder whether my question was rhetorical ...

Any chance of someone providing an idea for an installed price for a SB4000TL ? (more rhetoric I wonder :cool:)

Thanks
Z

A SMA SB4000TL Will retail around £1200.00 before 20% vat
ADD Labour cost so it still cheaper than the 25 year extension

zeupater

www.********.co.uk wrote: »

A SMA SB4000TL Will retail around £1200.00 before 20% vat
ADD Labour cost so it still cheaper than the 25 year extension

Hi

Which, including call out, travelling, fault diagnosis/testing, order, supply, margin, fitting, testing, paperwork, certificates and appropriate WEEE disposal of the replaced unit would equate to a ball park price to the customer, including VAT of ...... ??

Thanks
Z

www.mepelectrical.co.uk

1800 euro's for 25 years extension for a system <4KW.
& cost of Equipment will come down.

goldenspiral

Apologies for the length of this post. I ordered 16xAmerisystem 250W mono-crystalline panels recently, each with mini-inverter. Mini-inverters have a 25 year guarantee, eliminate DC loss and do not need replacing every 10 years. Most importantly for us, if one panel is shaded only the output of that panel drops. In a serial array all panels drop to the lowest, which might be 40%.

Total installed cost for 4kWh system is £14,500. The salesman knew his stuff. According to his officially approved figures it will produce 3432kWh pa and return around £66,500 over 25 years. This doesn't include an estimate on the price of electricity in 25 years time.

Sounds good, doesn't it? So why do I keep waking up worried? Here are my concerns.

Half the array will be on top of a flat roof, three floors up. The roof is bitumen felt with stone chips, 10 years old. If undisturbed it could last another 5-15 years. But if walked on to install equipment, I'm certain it will start to fail within 5 years. No point putting something guaranteed for 25 years on that, so add the cost of replacing now with fleece-backed EPDRM rubber, expected life 50+ years: £1,900.

The other half is going on a south-facing ground-floor roof with a shallow pitch (almost perfect) but shaded until 10am by the terrace of of which our house is part. By 11:15 the array will be in full sun. Depending on time of year, by around 16:00 shadows start to fall due to a neighbour's trees, clearing again for a short while in the evening for about 5 months of the year. So I assume this half will be producing a lot less than the calculated figures and when the sun is very low in winter the top half will also be less efficient (being only 10-degrees) and slightly shaded by a chimney stack with 2x4 pots.

So, first worry: how much efficiency am I going to lose and would going for thin film be wiser? They're less efficient but for various technical reasons not as prone to shading effects? Does anybody know? If I lose efficiency what will the true rate of return be?

For my calculations on the return I'm going to assume that for 66% of daylight, half the array is on 50% efficiency and for 33% on "full efficiency" (Govt. approved calcs assume 80% is full efficiency). So the return for that side is 33250((0.66*0.5)+(0.33*1))=33250*0.66=£21,945. For the other half I'm going to assume the chimney block causes a very minimal 5% reduction is 33,250-(66,500*0.5*0.05*1)=£31,587. Total return is £53,532, about the cost of the installation below what was quoted.

When the return was going to be £66,500 that was 10% pa which sounds great. But what would be the return on £14,500 in another investment, say the stock market?observationsandnotes.blogspot.com/2009/03/average-annual-stock-market-return.html says 9-10%.

And what's the annual return if the projected total is £53,532?

I found the formula here:
mathsisfun.com/money/compound-interest.html

i=((53,532/14500)to the power of 1/25) -1 = 0.0537 = 5.37%.

Hmmm.

Second worry: the lower roof also needs replacing, The builder put the wrong tiles on just three years ago, and died suddenly. At that point we discovered that "guarantees" really are worthless and it leaks badly. This new roof is the only essential cost. In rubber: £3,500 excluding internal redecoration and scaffolding. Total outlay: £20,340. Total non-essential outlay: £16,840.

We are going to finance this with money currently in an offset mortgage account. Although it doesn't earn interest, the effect on the mortgage is 5.99%. Loss of value to us is therefore 16840x5.99% = £1,009 pa.

Third worry: as all the panels are angled less than 30-degrees they need cleaning from time to time, especially after a dusty rainfall which we sometimes get in London. How will we reach the top ones? Fix rungs to the outside of the house? Build a hatch to climb out through the roof? I have no idea what those solutions might cost.

Pluses: when we pay off the mortgage in 12 years time we'll still have 13 years of tax-free return at 5.37%, index linked, plus the savings on what by then might be considerable electricity bills.
Minuses: we ultimately have to pay the capital back which is going to add a burden of between £1,208 and £3,625 pa, depending on whether we repay in 12 or 4 years.

One final factor: my wife will probably be getting a decent redundancy next year and wants to set up a business.

Should we hold on to the money and pull out of this deal? We're still in the cooling off period.