Cherrington et al. [28] show how recent changes to the FiT tariff for domestic-scale PV systems in the UK have changed the private viability of such technologies. They find that even major reductions in the applicable FiT rate from 43.3 p/kWh to 21.0 p/ kWh or 16.0 p/kWh delays the PBP by 2 years (12 years, rather than 10 years). While the return on investment falls, it remains “healthy” ([28], p. 421) at 7%. Muhammad-Sukki et al. [68] show how the payback period for solar PV projects differs across Europe with tariff levels, and that reductions in tariffs could have implications for the future deployment of such technologies.