Feed in Tariffs - Utility Recommendation
in Green & ethical MoneySaving
23 replies 5K views
This discussion has been closed.
Latest MSE News and Guides
Did you know there's an MSE app?
It's free & available on iOS & AndroidMSE App
Regifting: good idea or not?
Add your two cents to the discussionMSE Forum
Energy Price Guarantee calculator
How much you'll likely pay from AprilMSE Tools
When I registered with E.ON I only had to send a copy of my MCS certificate and a meter reading. No invoice was required.
Well that made me feel better and I'm about 100 miles North of you.
That message should be got over to those considering getting a free 'Rent a roof' system.
So many of them seem to think that their system will somehow power their storage heaters during the day!!! - and no doubt tumble dryer and all other appliances.;)
The best web site I have found for estimating the solar electricity generation is re.jrc.ec.europa.eu/pvgis/apps4/pvest.php
Thanks for mentioning the website - all the information I have on kwh production is from that web site. The estimates it gives for daily production based on the details of your system and location are surprisingly accurate (for the first 2 weeks of Nov that is).
People may be surprised that on a cloudy overcast day my 2.88kw systems produced only 100watts. The following sunny day (Nov) it produced 5,000 watts (5 Kw).
In summer I expect that it might produce up to 15,000watts (15kw) total on an very sunny day. I suppose you could say that at midday in midsummer the system may produce about 2,500 watts for the hour from 12 till 1pm (from a 2.88Kwh system less losses) less for each hour before and after - this may be a little optimistic! but the average in May is given as 11.10kwh per day.
The total for the year is estimated to be 2,380 Kwh.
2380 x 42.8p = £1,018.64. As I use nearly 9,000 Kwh per year (household of 7, 5 of them students) I expect to use most of this (say 75%) which would save me about 1785 x 10p = £178.50p.
Cost of installation £11,750 Return £1,197.14p
And Bristish Gas have just increased prices by 7% !!!
Hope this helps people who are thinking about investing in a system
A few people reported this summer that their peak kW output(around noon in June) exceeded their kWp value, so your 2.5kW from a 2.88kWp is not optimistic for systems where the siting is not compromised.
The low output you had for a cloudy day goes to show the big impact that shading has. My system is 1kWp smaller than yours and yet the lowest daily output I have seen so far is 500Wh - that was on a very dull and grey day.
In the summer your system could produce more than the 2.88kWp rated output if its unshaded and not limited by the rating of the inverter.
Many systems use an inverter with a lower rating than the panels max output, the idea being that the greater efficiency of a smaller inverter makes up for the losses on those few days in the summer when the output is very high.
Thanks for your post have found it very interesting especially the point about the use of smaller inverters - see below.
The bit about the effect of shading on an overcast day is not clear -see below. Would be grateful for your further comments.
The strange thing is of course on a very cloudy overcast wet day
there is no discernable shadow so don't think shading is a problem on such a day.
By the way these are the bad days (since 29/10/2010)
2/11/2010 = 200 watts
4/11/2010 = 100 watts
8/11/2010 = 300 watts
30/10/2010 = 5,100 watts
01/11/2010 = 4,800 watts
6/11/2010 = 4,900 watts
15/11/2010 = 4,400 watts
Be interested if you and others had the same good and bad days and was the difference as great between the worst and the best
Before installation during September I took many photos of the roof to see the effect of shading on roof 1 (South East facing). However whilst I am sure that during the summer months I have arranged the panels so that no panel is overshadowed after about 9am the sun has sunk so low in November (and will get worse until 21st December) that one of the panels is partly shadowed until about 1pm.
The other roof (6 panels south west facing) has a problem with a tree from next door. ( this did not seem a problem in September when the sun was higher. On a sunny day the leaves from this tree shade some of the panels for about an hour (around midday) and have noticed that the out-put from the panels halves during this time (from say 600watts per hour to 300watts per hour), This has no effect on an overcast day. The good news is that I have spoken to my neighbours and they are happy for me to chop down the last 15' of this tree (it may take a couple of years to grow back!). I have four trees in my garden which affect the panels from about 2pm - these I will have cut back this week as they have now lost their leaves. ( by the way I have about 14 trees in my garden some of which have preservation orders so these I can not touch). Much as I like trees they do grow very quickly and can shade everything and nothing grows beneath - not even grass.
The other point you mention is the inverters. I have 2 sunny boy sma 1200 inverters and questioned that I thought they should be sunny boy 1700 inverters. However I was given access to the free downloadable saftware:
This showed that for 6 phono-solar panels 240watt the sma 1200 was more efficient than the sma 1700. So from the inverters their max outpout is 1200watts each - and they are only 92% efficient.
Once you get solar panels you take a lot more notice of how the sun tracks in the sky, surprising just how low it gets in the winter.
Assuming that the figures you posted are Watt Hours and not just Watts then I would say what you are getting is fairly typical.
In the winter months the out put can vary a lot - in your case as low as 0.1kW and as high as 4.4kW. Still at least it proves the point that solar panels do work in the winter in the uk.
This link to the kyocera website gives a very good explanation of why shading has such a big impact on the panels:
I get some shading on my panels late in the day, but only in the winter months. I knew before I went ahead with the panels that this would be there, but happy to accept a small loss of output over the winter.
Thanks for the link to the website it was very informative