BASIX assesses photovoltaics as an alternative energy source based on the total rated output of all panels, expressed in kW. The rated output of an individual photovoltaic panel can be found written on the back of the panel. If the rating is not shown on the panel, the manufacturer or supplier of a system should be able to advise you of the rated output for the particular system.
A photovoltaic system (PV) is a type of energy system consisting of flat panels, typically made from silicon, which are installed in an unshaded location. These panels capture sunlight and convert this into electricity which can be used in your home.
Photovoltaic system size is generally limited by both cost and availability of suitable unshaded space. It is common to install a smaller photovoltaic system that meets only part of the total electricity demand of the building.
Before installing a photovoltaic energy system, ensure your home is designed as efficiently as possible. Many energy efficiency measures will be more cost-effective in reducing greenhouse gas emissions than a photovoltaic system.
Ensure that the area where the PV panels will be located is completely unshaded – shading of even part of a panel can greatly reduce output. Also ensure the panels are sloped at an appropriate angle and correctly orientated – the wrong slope or orientation can reduce annual output of power. Check the development controls relevant on the land neighbouring your house. It may be possible that your neighbour is permitted to construct a taller dwelling, which may overshadow your photovoltaic panels. Speak to your neighbours to see if they have any plans to redevelop their property in a way which may affect your solar access.
Aesthetic considerations are usually important when installing a photovoltaic system, and it is common for a system to be installed flush to the roof at a non-optimal slope, and even incorporated directly into the building fabric as roof tiles, in order to ensure the panels as unobtrusive as possible and do not detract from the appearance of the building.
Consult with your photovoltaic system supplier to determine the most appropriate system for your needs.