#1 April 19, 2013 18:28:00

Telegram Sam
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Basics for beginners


Can I ask for clarification of some basics - as someone who is pondering the pros and cons before rather than after taking the decision to go solar (or is that cheating?)


1. I take it that I CANNOT use the database to assist in a choice between one brand of panel and another?


2. I am dubious whether it will assist me to choose between one system type and another - thin panel vs crystalline being the two main contenders as far as I understand it.  It seems that the former is technically more efficient but comes with a cost penalty.


3. Can I however use the database to judge what annual kwh's users of one or other system are actually achieving in geographical and physical locations comparable with my own?  This would seem to be in the spirit of the thing but just how to implement it with reasonable accuracy is not totally clear.


4. There are various online spreadsheet calculators designed to convert the inputs into payback periods etc.  Any one in particular to recommend?


Thanks





Edited Telegram Sam (April 19, 2013 18:28:00)

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#2 April 21, 2013 11:52:00

rogerhoward
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Basics for beginners


No to each.


But potential installers are in any case required to present the predicted generation of a site's system from a standard model calculation. Predicted generation should be the same from them all, and it's not something that you need to calculate yourself.


The cost of normal efficiency panels has reduced so much that nowadays the main cost is that of the installation, almost regardless of size.


So the initial question is simply “how big a system can be fitted onto the roof(s)”? A year ago, I went about it as follows.


1. Go into the loft and measure the size of the useable roof(s).
2. Draw the roof(s) on paper or computer.
3. Assuming a size of 1m x 1.6m for standard cheap “15% efficiency” 250W panels, how many can be fitted onto the roof(s) diagram? (As near as possible to 16 x 250W panels is the objective.)
4. Is it significantly less than 16 panels? If so, hunt around online for the sizes of higher powered panel makes, say “20% efficiency” like the Sanyo FiT, and repeat point 3 with the alternative sizes of those more specialist panels. N.B. I didn't have to go around this loop - can someone else add something about the effect of higher efficiency panels on predicted generation figures?
5. By now you should have some idea of the possible size of your likely PV system. Enter it into an online calculator to get the likely annual generation. (As mentioned before, calculators should all give the same result, but note that they take Sheffield as their “solar irradiance” benchmark.)
6. From the predicted annual generation figure, calculate the corresponding annual FiT payments.
7. The amount to be added onto the FiT payments for electricity usage “saved” is debateable. Without an export meter, even us folks with PV systems typically only have a rough idea from comparision with our pre-PV electicity bills. But the more electricity being currently used, the greater the likely saving. Here, I call it a fifth of my previous usage.
8. I just looked for suppliers who could do my system for less than 15 times the predicted annual FiT payments. I think we all know that electicity cost inflation is going to be higher in the future. But a payback-period calculation calls for finger-in-the-air, your-guess-is-as-good-as-mine assumptions about future inflation of both FiT payments (calculated at the general inflation rate) and the normally higher electricity cost inflation (for the electricity usage saved). If we did this assessment for double-glazing we'd find that we'd be long dead before the double-glazing paid for itself, but we go ahead regardless as an insurance policy against future rising energy costs, don't we? I don't know why the same attitude isn't taken with micro-renewables really.
9. Proceed with contacting the most suitable supplier, armed with all the above preferably plus roof photo(s) emailed to them, so that both parties are aware of expectations ahead of the site visit.


My installation cost was only 12 times the predicted annual FiT payments. Including “electicity saved”, and at currently modest inflation levels, my packback period will be about 8 years.


There are plenty of solar systems installed in the 1970s that are still going quite happily. Looking into the crystal ball beyond the FiT payments era, who knows what level electricity prices will have reached by then? I don't think any of us here with PV systems would now want to move to a property without one.


Hope this helps.







Economy 10 tariff provides 6.9p/kWh off-peak import between 12am-5am, 1pm-4pm and 8pm-10pm; http://www.pvoutput.org/aggregate.jsp?id=21047&sid=18934&v=2&t=m on approx. 63% off-peak usage, 22% solar usage, and 15% peak-rate usage.
1,900kWh annually is exported, mostly in summer, on approx. 3,200kWh generation. Approx. 4,500kWh/year is imported, mostly for (a) winter and springtime off-peak Storage Heaters, and (b) off-peak hot water Immersion heating (which is “dumb”, i.e. not linked to the solar PV).
PV array is split East-West. Income is from Phase II 21p/kWh Feed-in-Tariff plus smart metered 3.2p/kWh Export Tariff.

Edited rogerhoward (April 21, 2013 11:52:00)

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#3 April 21, 2013 13:43:00

Telegram Sam
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Basics for beginners


Many thanks for this useful information.  To a large extent I have already trodden the path you have described and fortunately the question of roof size is not an issue.  There is adequate space for a 4 kW system (and more though I understand that it is not economic for private households to go above this)


 


The crunch I was (and am) faced with having spoken to several interested installers is what annual output generation figures to base calculations on and this is where it really becomes smoke and mirrors.  It seems that the gospel SAP comes in more than one “issue” depending on the date, some are more credible than others (apparently), and many installers maintain that SAP is way too conservative anyway - for mono-crystalline and even more so for thin panel technology.


 


 


 


 


 


 


 


Like you I took the claimed savings from own consumption with a pinch of salt and base the economics of the system mainly on the FIT. That said I believe in making some assumptions and crunching the numbers through on a spreadsheet just to get a feel of the orders of magnitude.  The fact that the investor is likely to be out of pocket initially for the likes of (I agree) 8 years is I suspect something that is lost on many who just look at the annual returns!  As someone said PV loses out to ISA's in the short to medium term, but compared with putting money into a pension annuity at present dismal rates does have its long term attractions!


 


 


 


 


 


 


 


I think your last sentence is the one to focus on.








Edited Telegram Sam (April 21, 2013 13:43:00)

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#4 April 21, 2013 16:32:00

rogerhoward
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Basics for beginners


Sorry that wasn't helpful, TS. Not satisfied with the SAP prediction then?


Taking all the ups with the downs this past 11 months, my actual generation looks like coming in at 3% above SAP annual predictions. That's despite the peak generation months of last June and July both being notably poor last year, see http://www.metoffice.gov.uk/climate/uk/anomacts


I don't know whether the SAP is just conservative, or your quoted “way too conservative”. But elsewhere on this forum, you can find PVers mentioning their ongoing generation predictions using the independant “PVGIS” tool; http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php I don't personally use it because I have an unusual East-West configuration, but others here use it all the time.


Maps of Solar Irradiance that I mentioned can be found all over the web.


If you do have space for 4kW, there must be installers your way who can make it pay for you - otherwise they'd be wasting their time being in the domestic market. The installer who did mine is advertising my 4kW system for £6k now!


Personally I consider my PV system not just an insurance policy against future rises in electricity prices but (as I'm in my 50s) as an early pension, the income being handily inflation-linked for the future. If you know of any alternative investment that gives a similar gauranteed return with inflation-linking then I'm all ears, believe me.







Economy 10 tariff provides 6.9p/kWh off-peak import between 12am-5am, 1pm-4pm and 8pm-10pm; http://www.pvoutput.org/aggregate.jsp?id=21047&sid=18934&v=2&t=m on approx. 63% off-peak usage, 22% solar usage, and 15% peak-rate usage.
1,900kWh annually is exported, mostly in summer, on approx. 3,200kWh generation. Approx. 4,500kWh/year is imported, mostly for (a) winter and springtime off-peak Storage Heaters, and (b) off-peak hot water Immersion heating (which is “dumb”, i.e. not linked to the solar PV).
PV array is split East-West. Income is from Phase II 21p/kWh Feed-in-Tariff plus smart metered 3.2p/kWh Export Tariff.

Edited rogerhoward (April 21, 2013 16:32:00)

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#5 April 21, 2013 16:58:00

rogerhoward
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Basics for beginners


The amount of electricity usage that you save is probably also affected by your lifestyle. With me being at work daytime weekdays, it's only at weekends that I get any benefit, hence my only “one fifth” reckoning here.










Economy 10 tariff provides 6.9p/kWh off-peak import between 12am-5am, 1pm-4pm and 8pm-10pm; http://www.pvoutput.org/aggregate.jsp?id=21047&sid=18934&v=2&t=m on approx. 63% off-peak usage, 22% solar usage, and 15% peak-rate usage.
1,900kWh annually is exported, mostly in summer, on approx. 3,200kWh generation. Approx. 4,500kWh/year is imported, mostly for (a) winter and springtime off-peak Storage Heaters, and (b) off-peak hot water Immersion heating (which is “dumb”, i.e. not linked to the solar PV).
PV array is split East-West. Income is from Phase II 21p/kWh Feed-in-Tariff plus smart metered 3.2p/kWh Export Tariff.

Edited rogerhoward (April 21, 2013 16:58:00)

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#6 April 21, 2013 17:25:00

Telegram Sam
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Basics for beginners


It was helpful but the topic is none the less not simple.  Faced with conflicting claims I am now investigating a separate database of what local PV users have actually achieved and recorded up here in the North East, which strikes me as the pragmatic way to do it. I had hoped to do this via Microgen.


I had a look at your PGVIS tool and whilst fascinating I reckon it is more a tool for the installers of this world, rather than Joe Soaps without degrees in meteorology, not forgetting of course the qualified participants of this forum!  It will take me more mental effort to get to grips with it.


My lifestyle and conclusions are similar to your own.


If the Stars say that the PV investor is going to stick around (in his PV house) long enough to reap the returns of his investment, and the Treasury doesn't run out of funds and change the rules (never ..), then like you I'd like someone to come up with a better choice.  Trouble is that if before then he or she ends up in an old folks' or convalescent home then all the PV the sun will afford us ain't going to pay the bills!











Edited Telegram Sam (April 21, 2013 17:25:00)

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#7 April 21, 2013 18:10:00

rogerhoward
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Basics for beginners


There's no need to worry about the Treasury's lack of funds. The FiTs are met by the ‘leccy companies, and passed onto the consumer (so you’re not a Daily Mail reader, then?!)


I can't speak for them, but it may indeed be that once back next week, the Sheffield Solar Farm have some emerging thoughts on the extent to which the SAP is conservative. There might even be something elsewhere on this forum. But meantime your idea of consulting your local database of achieved generation sounds really excellent and just what you need.


You seem to have successfully gathered that in your position the hardware technicalities are nothing to get hung up on. When all's said and done a 4kW system with a fancy brandname and state-of-the-art spec is still just a 4kW system.


The reason that I described the FiT as “gauranteed” return is that despite the ups and the downs of the weather I have the feeling that generation/returns are relatively predictable actually. A pension fund - yes a pension fund - recently bought a bond issue from the new Westmill Solar Farm, the returns were so relatively predictable.


Then again on a longer time scale, I suppose it's possible that we could get more atmospheric precipitation and regular wild storms resulting from global warming that puts all the predictions into the scrapheap! Can't plan anything in life on the basis of the unknowable though, can you? I too could possibly move once retired or may end up in an old folks home, as I don't have any kids.







Economy 10 tariff provides 6.9p/kWh off-peak import between 12am-5am, 1pm-4pm and 8pm-10pm; http://www.pvoutput.org/aggregate.jsp?id=21047&sid=18934&v=2&t=m on approx. 63% off-peak usage, 22% solar usage, and 15% peak-rate usage.
1,900kWh annually is exported, mostly in summer, on approx. 3,200kWh generation. Approx. 4,500kWh/year is imported, mostly for (a) winter and springtime off-peak Storage Heaters, and (b) off-peak hot water Immersion heating (which is “dumb”, i.e. not linked to the solar PV).
PV array is split East-West. Income is from Phase II 21p/kWh Feed-in-Tariff plus smart metered 3.2p/kWh Export Tariff.

Edited rogerhoward (April 21, 2013 18:10:00)

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#8 April 21, 2013 19:50:00

guava090
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Going for a solar pv system is a no brainer even at the present lower rates!!! And if you do!!!!! make sure you fit power optomisers see the solaredge web site.



Guava 090.



Edited guava090 (April 21, 2013 19:50:00)

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#9 April 21, 2013 20:22:00

rogerhoward
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Basics for beginners


Good to see someone else coming in on this.


You said it there,  guava090. TSs number-crunching surely must be showing him that too, but suspicion frequently rules.


A Cash ISA even in the short-term gives pitiful returns by comparison, and an investment ISA isn't a low-risk valid comparison at all. The real comparison is with annuity rates, which TS agrees are dismal. Being “out of pocket” until your investment matures is hardly the way anyone feels about their other investments, still less about the thousands people spend on their properties without any return at all. How much would double-glazing cost with a sometime-never return?


Is DennisG from the North East still around with his 2.6kW system generation figures for comparison? He had apparently achieved 200kWh more than predicted in his first 6 months in 2011 last time I heard.







Economy 10 tariff provides 6.9p/kWh off-peak import between 12am-5am, 1pm-4pm and 8pm-10pm; http://www.pvoutput.org/aggregate.jsp?id=21047&sid=18934&v=2&t=m on approx. 63% off-peak usage, 22% solar usage, and 15% peak-rate usage.
1,900kWh annually is exported, mostly in summer, on approx. 3,200kWh generation. Approx. 4,500kWh/year is imported, mostly for (a) winter and springtime off-peak Storage Heaters, and (b) off-peak hot water Immersion heating (which is “dumb”, i.e. not linked to the solar PV).
PV array is split East-West. Income is from Phase II 21p/kWh Feed-in-Tariff plus smart metered 3.2p/kWh Export Tariff.

Edited rogerhoward (April 21, 2013 20:22:00)

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#10 April 21, 2013 22:41:00

guava090
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Basics for beginners





My system returned an ROI of 11.96% last year with a 3.5% int added to the cap.


Guava. 





Edited guava090 (April 21, 2013 22:41:00)

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