Not quite. In the UK, you need a professional installer. Obviously, that adds labour costs. But you'd have to pay for the scaffolding etc anyway. With anything electrical, you should get a certified and insured professional to do the installation and sign it off. Payback time is complex. Different countries have different subsidies available. We expect the system to pay for itself in 10-15 years. But I'm more concerned about the ecological impact than the economical one.