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Predicted Feed In Tariff

I was wondering if anyone who has had solar PV for a long time been able to compare their actual to predicted generation. Has anyone got significantly less than predicted or significantly more or are the predictions fairly accurate? My system is too early to predict as it's only been in operation a few weeks but if anyone has had a system in excess of a year the results would be interesting.
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  • There is a website that will predict what output you should have for the location, size of installation etc.
    http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php
    Remember to search for your location first.
    I have had my 2.88 installation since the 1st Nov.
    Best day's output 4.8Kwh on 01/11/2010
    Worst days output 0.01Kwh on04/11/2010

    After 21 days I have produced 48.2 Kwh's of electric
    average per day = 2.29Kwh's
    From the website I should average in November 2.26 -2.4 Kwh
    So I'm fairly happy

    Two of my close relations have each had their installations completed on Friday 19th Nov.
    On the 20th Nov
    one has a 3.96 installation and produced 3.6kwh (no shading)
    the other has a 3.12 installation and produced 1.39kwh (some shading - next doors house)
    and I have a 2.88 Kwh system and produced 1.56Kwh (some shading - next doors house and tree)

    I have the daily output since 1st Nov if you are interested.

    We are located within 5 miles of each other.
    Graham
  • Before I bought a 3.96KWp PV system, I used http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php to estimate my expected generation. The result was 3076KW per year (this was also broken down into predicted generation each month). The supplier of my system predicted a total generation amount of 10% less.

    My system was installed in May 2010 and so far generation has exceeded the 'Europa' prediction every month. After 7 months, cumulative generation is 21% above the prediction for those 7 months. If this performance continues the system should generate around 3600KW in its first year. This would give me a 9.5% tax free return on the capital invested!

    Scottish Power have paid the FIT and export amount promptly each quarter.

    I live in north Cumbria and the roof is about 40 degrees west of south. The hours of sunshine recorded for NW England have been around average over this 7 month period.

    So far I am very pleased with the performance of the system.:j
  • CardewCardew Forumite
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    redbottle wrote: »
    Before I bought a 3.96KWp PV system, I used http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php to estimate my expected generation. The result was 3076KW per year (this was also broken down into predicted generation each month). The supplier of my system predicted a total generation amount of 10% less.

    My system was installed in May 2010 and so far generation has exceeded the 'Europa' prediction every month. After 7 months, cumulative generation is 21% above the prediction for those 7 months. If this performance continues the system should generate around 3600KW in its first year. This would give me a 9.5% tax free return on the capital invested!

    Scottish Power have paid the FIT and export amount promptly each quarter.

    I live in north Cumbria and the roof is about 40 degrees west of south. The hours of sunshine recorded for NW England have been around average over this 7 month period.

    So far I am very pleased with the performance of the system.:j

    Interesting post - I think the only one I have read where performance is considerable above prediction. Most predictions seem pretty accurate.

    Middle England seems to get around 800kWh to 850kWh per kWp, so if you get 900kWh in extreme NW England, with a roof at less than the optimum orientation, it will be an eye opener.
  • redbottle wrote: »
    Before I bought a 3.96KWp PV system, I used http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php to estimate my expected generation. The result was 3076KW per year (this was also broken down into predicted generation each month). The supplier of my system predicted a total generation amount of 10% less.

    My system was installed in May 2010 and so far generation has exceeded the 'Europa' prediction every month. After 7 months, cumulative generation is 21% above the prediction for those 7 months. If this performance continues the system should generate around 3600KW in its first year. This would give me a 9.5% tax free return on the capital invested!

    Scottish Power have paid the FIT and export amount promptly each quarter.

    I live in north Cumbria and the roof is about 40 degrees west of south. The hours of sunshine recorded for NW England have been around average over this 7 month period.

    So far I am very pleased with the performance of the system.:j

    That's excellent performance you getting, could you provide some more details - which panels and inverter and more importantly, what angle (pitch) is your roof?

    So far my system is pretty much bang on the estimated output, it's actually quite surprising how accurate the estimates for solar pv are.
  • Jon/Cardew

    My system consists of 18 X Sharp ND220E1 Polycrystallline PV panels connected to a Diehl Platinum 3800S inverter. The roof has an inclination(pitch) of 25 degrees and as I stated above faces about 40 degrees west of south.

    Best days generation so far was 27.9kW on 22 June (close to longest day!)
    Worst days generation so far was 0.4kW on 17 November.
    For the first three months (May-Aug) I also had the benefit of a winding back meter, during these months we imported no electricity (despite using the electric immersion heater for hot water). My meter was replaced in September.

    Cardew's comments reference expected performance were reflected in my installers estimate of performance. They have experience of systems in the north of England and as a rough rule of thumb expect about 700-750kW per annum per 1kWp installed.

    However from 11 May until today (6.5 months) my system has already generated 2480 kW. (625kw per 1kWp installed).
  • I had a small 1.32 kWp system installed on 5th October consisting of 6 Sharp 220 panels and a Sunny Boy 1200 inverter. Roof pitch is 30 degrees and faces due south.

    Installers estimated that I would get 1000 kWh per annum whereas calculations on the europa web site predict that I should get 1120 kWh.

    During the shortened October the system generated 81 kWh against a prediction of 75.1 kWh on the web site for the full month and to date during November the system has generated 35 kWh (full month prediction on the web site is 42.7 kWh).

    Day time electricity usage has been reduced by one third on average since the installation. I am at home during the day and I have an old style "spinner" meter which runs backwards.

    I'm happy with the performance so far but would like to see a full years data, especially over the peak Summer months.
  • redbottle wrote: »
    Jon/Cardew

    My system consists of 18 X Sharp ND220E1 Polycrystallline PV panels connected to a Diehl Platinum 3800S inverter. The roof has an inclination(pitch) of 25 degrees and as I stated above faces about 40 degrees west of south.

    Best days generation so far was 27.9kW on 22 June (close to longest day!)
    Worst days generation so far was 0.4kW on 17 November.
    For the first three months (May-Aug) I also had the benefit of a winding back meter, during these months we imported no electricity (despite using the electric immersion heater for hot water). My meter was replaced in September.

    Cardew's comments reference expected performance were reflected in my installers estimate of performance. They have experience of systems in the north of England and as a rough rule of thumb expect about 700-750kW per annum per 1kWp installed.

    However from 11 May until today (6.5 months) my system has already generated 2480 kW. (625kw per 1kWp installed).

    Thanks for the extra info, very interesting. I note that you have polycrystallline panels where most people seem to go for mono, mainly due to wanting the maximum size system for the available space - I wonder if this is a factor?

    Either way, you are getting excellent results, you must be very pleased!
  • CardewCardew Forumite
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    redbottle wrote: »
    Jon/Cardew

    My system consists of 18 X Sharp ND220E1 Polycrystallline PV panels connected to a Diehl Platinum 3800S inverter. The roof has an inclination(pitch) of 25 degrees and as I stated above faces about 40 degrees west of south.

    Best days generation so far was 27.9kW on 22 June (close to longest day!)
    Worst days generation so far was 0.4kW on 17 November.
    For the first three months (May-Aug) I also had the benefit of a winding back meter, during these months we imported no electricity (despite using the electric immersion heater for hot water). My meter was replaced in September.

    Cardew's comments reference expected performance were reflected in my installers estimate of performance. They have experience of systems in the north of England and as a rough rule of thumb expect about 700-750kW per annum per 1kWp installed.

    However from 11 May until today (6.5 months) my system has already generated 2480 kW. (625kw per 1kWp installed).

    This raises a question that I have pondered!!! How accurate are the meters?

    On the face of things your output is just not achievable - especially as you have an underated inverter - max output 3.6kW(it is quite normal to have this)

    What is the maximum power kW - not kWh you have seen from the system?

    I would have thought that a meter must be tested to very stringent standards.

    P.S.

    You have checked there are only 18 panels on your roof?;)
  • My inverter is in the loft so I don't usually see the instantaneous power it is producing. I do however have an Owl type meter which gives me the net flow in/out of my house, though I understand these are not very accurate. This meter has peaked at about 3.8kW at times in June, when I was not using any significant power in the house.
    There are 18 panels on my roof!:p

    I'll post more data when I have a full 12 months in May.
  • I'd be very surprised if anyone in the country didn't achieve the figures they have been quoted as the government guidelines for calculating the output of solar systems (SAP) is very conservative. For example, in the North of England they assume the panels will only operate for 1,000 hours per annum (less than 3 hours per day) and up in Scotland it's even worse; only 800 hours per annum.

    Apart from the orientation and angle of your roof surface, where you live and any shading factors (adjacent trees or larger buildings, etc) the equipment itself plays an important part and will therefore also account for local variations.

    As has been said previously, mono panels are superior to poly and the inverter output is a vital factor too. For example, many inverters which have been fitted in the UK to date operate at 200volts. In simple terms this means that it doesn't switch on in the morning until your solar panels collectively are generating at least 200 volts and similarly in the afternoon the inverter will switch off once the voltage drops below 200 volts again. There are some inverters that switch on and off at only 125 volts; therefore prolonging the period during which the solar system generates electricity.

    Lastly, let's not forget the price of the overall system. I've seen quotes from large national companies (I will name no names) charging £22,000 to fit a 4kw system. I know these can be supplied and installed (with mono panels and a good invertor) for less than £14,000.

    Do your homework before you buy a pv solar system as the price you pay initially can have a huge bearing on how long it will take you to recoup your original investment.
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