*A 4kW PV system will typically generate between 3,400 and 3,800 kWh per year in the South Wales region. Over a 20 year period that’s between 68,000 to 75,000 kWh of electricity supplied by you. At a typical cost of £4,700 (currently no VAT until 2027), that equates to a unit price of less than 7.5p per kWh if you use all the power generated.