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What are the rules about extending my solar panels?

Posted by Cathy Debenham on 25 April 2014 at 11:28 am

Q: I have a 3kw solar PV system installed for 3 years now. Originally the roof suffered from shading but I have now removed a tree so could fit another one or two panels. I purchased an extra two panels originally as spares. Could I fit these (using an accredited fitter) and claim the feed-in tariff (FIT) on the new rate for the extra panel? (I don't need to change the inverter as it's within the tolerance with the extra panel). Would I need an extra export meter for the extra panel or could it be calculated pro-rata?

A: The FIT guidance document defines an extension as a 'modification to an accredited installation to increase its total installed capacity (TIC) from the same eligible low-carbon technology'.

With the exception of stand-alone installations, extensions to solar PV installations after 1 April 2012 must meet the new energy efficiency criteria to receive the higher rate of tariffs. ie your home must have an EPC of D or above.

The way it works is that the extension is assessed as a separate eligible installation. If it's successfully accredited, the extension will be assigned a separate eligibility period (20 years from eligiblity date) and separate tariff code based on the aggregate TIC of both existing and new installations. In your case, 3kW + 2 new panels would still have you in the same bracket of up to 4kW, but you'd get the 14.38p generation tariff current now on the 2 additional panels, rather than the higher rate you got before.

I checked with Ofgem what the requirements are. These are the things you must bear in mind:

·         You will need to apply for the extension in the same way as you did for your original installation via your FIT Licensee.

·         You will need to provide the same documentation for the extension as for your original installation.

·         The rules regarding Energy Performance Certificates (EPC) apply equally to the extension. That is, the EPC must be issued within 10 years of commissioning.

·         The eligibility date for the extension is the commissioning date and not the application date as per original installations.

·         Where the original installation and the extension share the same generation meter and (if applicable) export meter, the FIT payments will be pro-rata based on respective capacity. E.g. if the original installation has a capacity of 3kW and the extension 2 kW, two fifths of the generation will be allotted to the extension, the same applies for export where the generator has opted in to receive FIT Export Payments.

·         The extension will have its own eligibility period accruing from the commissioning date so it is essential that the start meter read is captured on the eligibility date. The eligibility period of the original installation will not be affected.

·         The extension will have its own tariff rate based on the date of commissioning.

·         The tariff rate assigned to the extension will be based on the combined capacity of both the original and the extension. The original extension will not have its tariff rate amended. E.g. (using the figures above) the original installation will remain on the 0-4kW tariff rate applicable to its eligibility date where as the extension will be assigned the applicable tariff rate for its eligibility date in the 4 – 10 kW tariff band. That is to say that if the original installation has an eligibility date of 3 Apr 13 it will be paid 15.86p/kWh for generation and if the extension has an eligibility date of 3 Apr 14 it will be paid 13.03p/kWh for generation.

Further detail and guidance is available in Ofgem's guidance document but your FIT Licensee (the energy company you get your FIT payment from) should be your first port of call for queries and assistance.



Photo: Edmund Tse


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