Adding Solar Panels to your roof

The use of solar panels on the roof space is getting more attention lately as the costs have come down the last few years.

Under the Building Regulations – Part L there is minimum level of energy provision from renewable energy technologies. There is three ways to meet these minimum guidelines:

  1. 10 kWh/m2 /annum contributing to energy use for domestic hot water heating, space heating or cooling;
  2. or – 4 kWh/m2 /annum of electrical energy;
  3. or – a combination of these which would have equivalent effect

In this analysis I am looking at Option 2 to meet the buildings regs for a new build. The manner on which i propose to do this is by means of PV panels. (PV-solar photovoltaic)

Taking the standard size of a Semi-detached house, two-storey with a total floor area 110m2 the minimum electrical energy that must be produced a year is 440 kWh.

To achieve this output it will require two of the 260W peak PV panels. The total area required on the roof for this is 3.27m2. The additional weight on the roof due to the panels is 37kg.

Taking the Irish national average electricity consumption of 5,300 kWh per annum part L has meet 8.3% of its needs. The typical cost of this energy usage generated by the PV would be 75 euro per annum. The avoided CO2 would be 210kg of carbon a year.

Of course you don’t need to be building a new build to add PV panels to your roof. You can do this on an existing property. The cost of two additional panels is less than €600 using a quoted price of supply, install and commission price of 1.20 euro a watt. In bulk this can be reduced to less than €500, not much of an impact on the bottom line. If you want 4 panels you are looking at a cost of somewhere between 1500-2000 by the time the additional works are done. This would be a valuable addition to any roof though.

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