How to Monitor the Performance of Your PV System

Do you know if your PV system is performing as well as it should? Do you know if your system is performing as well as other local PV systems? Are you interested in comparing the performance of your system with others in the UK.

Well it is relatively simple to answer all of these questions.

When you had your system installed your installer had to give you an estimate of what your PV system should generate in an average year. This is known as a SAP calculation. The SAP calculation calculates the output of a solar PV system according to the Government's Standard Assessment Procedure for Energy Rating of Dwellings (SAP 2005). This assessment takes into account such factors as shading, orientation and angle of the solar panels. It is usually quite conservative and don't take account the precise whereabouts of your property.

So as a starting point you have the installers estimate to compare your actual output.

However the PV output varies throughout the year due to the height of the sun and the length of the days among other climatic factors. It is very helpful to know what your system should be generating on a monthly basis so that you can compare your actual generation figures with a monthly estimate. Such monthly estimates can be obtained from the PVGIS website. Help in using the PVGIS calculator can be found on site.

So now you can compare your actual PV output figures with a monthly estimate specific to your actual latitude and longitude.

Finally there are organisations who collate data from hundreds to thousands of individual subscribers, enabling those subscribers to compare their systems overall performance with other individuals locally or in other parts of the world. One such website is :-

The Microgen database organised by the University of Sheffield, also known as the Sheffield Solar Farm. This website offers a wide range of comparisons, a forum to ask questions and a monthly report.

So now you can compare your actual output with other local PV generators which will help you evaluate whether local weather conditions for example are impacting your output.

The University of Sheffield have developed an application with enables you to compare the annual generation predicted by SAP, PVGIS and the Sheffield Solar Farm's database.

You will need your installation's location by longitude and latitude. To find these figures from your postcode, you can use public tool: http://www.doogal.co.uk/ShowMap.php?postcode=EX17 4HG but add your own postcode to the end. 

So with all this potential data and comparison sites it should be possible for you to evaluate whether your system is performing properly. If it is not, then you should contact your installer.

Information about the Green Deal

We have put together some information which explains what the Green Deal is all about. Essentially its is a long term loan (10 to 25-years) to undertake specific energy saving measures in home and is repaid through savings in your utility bills. Read much more on our Green Deal webpage.

Solar PV Project has Ended

Solarsense, our PV Panel installer, informed us at the start of June that they did not want to extend our agreement for another year. The first year of the agreement saw an impressive 72 installations. However by the start of the second year feed-in tariffs had halved and the public's interest in PV panels generally waned even though there is still a 10% tax free index linked financial return on an investment in PV panels. In the second year only one more set of panels was installed, so we have agreed that it hardly seems worth carrying on. Solarsense have been impacted by the downturn and have laid off staff. However they are diversifying into heat pump and biomass installations and are continuing to be a viable company, unlike many other PV suppliers.

Warm Homes Project has Ended

Our Warm Homes Project ended on the 30th June, having been extended by the government for three months to allow participating community groups to finish off any outstanding installations. We were offered upto £40,000 in grants by the Department of Energy and Climate Change to install renewable heating systems in our area. We had interest from about 20 Sustainable Crediton supporters, most of whom received free home energy performance assessments and renewable energy assessments. However only eight homes had systems installed ( 5 air source heat pumps and 3 solar thermal panel systems) resulting in our taking up only £12,000 of the available funds.

However there is some good news in that the Government have announced that the upfront grants known as the Renewable Heat Premium Payments have doubled for all renewable heating installations. The new grants are as follows:

Ground source heat pumps £2300

Air source heat pumps £1300

Biomass boiler £2000

Solar Thermal £600

It is likely that the Renewable Heat Incentive payments will come into being from Spring 2014.