Policy risk is frequently highlighted as one of the most significant risks facing investors in sustainable energy and has a significant role in dissuading investors from allocating capital to this sector (Parhelion, 2012, Micale et al., In particular, retroactive policy change risk is highlighted as a principal concern as it directly impacts expected and historical revenues from projects and lowers investor confidence in the stability of the financial support available over the investment lifetime (Parhelion, 2012, Frisari et al., Government could pre-commit to reduce these risks, e,g, through contractual penalties in the case of material policy changes.