No two projects are the same. However, ball park figures for fully installed costs are:
£4,000-£8,000/kWp for a 1kW roof mounted system (the Energy Saving Trust show the average installed cost to be £5,000)
£8,000-£15,000/kWp for façade or atrium systems, typically for prestige or architectural designs requiring specialised design.
There are economies of scale to be had, both in size of solar PV system and number of systems bought. For example, Enviko have provided a 10% reduction for a 5kW system and a 20% reduction for a 50kW system (from the 1kWp system price). Discounts are negotiated on an individual basis with our customers, dependent upon an initial site-survey and/or pre-feasibility study.
The size of a photovoltaic installation is expressed by its kilowatt peak (kWp) potential, which is an indication of how much electricity the system could generate at peak or optimum conditions. As a rough rule of thumb the Department of Trade and Industry (DTI) estimates that a typical 1kWp system in the UK could be expected to produce between 700-750 kWh/year of electricity, although some technologies will generate considerably more than that. A high performance system in London might be expected to produce a maximum of 850kWh/year.
A gas heated 2 bed/4 person flat (built to 2002 Building Regulations) uses approximately 1,500kWh/year in electricity (for lights and appliances), so a typical 1kWp system would provide approximately 45% of the dwelling’s electricity needs.
A gas heated 4 bed/7 person 3 storey terraced house (built to 2002 Building Regulations) uses approximately 2,500kWh/year (for lights and appliances), so a typical 1kWp system would provide approximately 28% of the dwelling’s electricity needs.
From the DTI domestic field trial performance analysis of 113 domestic systems, the average contribution of a PV system to the electrical load has been 43%. The contribution clearly depends on the size of the system installed but is also a function of the available sunlight throughout the year.