Do you get the depreciated value added on to the house price if you sell? This was always a big problem for solar hot water systems. If the payback period is seven years but the average house turnover is five years, then there is little incentive.

Gov subsidies are the government giving the tax money of poor people who cannot afford houses to rich people who have houses. Highly regressive. Your PV system should stand on its own merits without holding out your hand to other taxpayers to fund you.