This study examines the cost-effectiveness of residential photovoltaic (PV) systems in the UK by considering the changes occurring in the supporting mechanism, the Feed-in Tariff (FiT). The metric used is the levelised cost of energy. The analysis stresses the importance of the FiT scheme and demonstrates the lowest cost of produced energy that domestic PV systems can achieve with the current policies. In this study, the term grid parity is used when the levelised cost of the PV generated energy is lower than the retail electricity cost that the consumer pays. It is observed that, for certain scenarios and in certain UK cities, a domestic PV system can reach grid parity without using the FiT scheme, but it might not constitute a sufficient reason to invest in a PV system.