The fastest way to improve your solar panel payback period is to maximise generation per square metre of roof, because the panels themselves are only about 5 to 10% of total system cost. The labour, scaffolding, and inverter stay roughly the same whether you fit a modest array or fill the roof, so the real question is not how cheap the panels are but how much electricity each metre of roof can produce. Get the design, the installer, and the post-install setup right and a well-configured system can repay itself in six to seven years in southern England.
