How the variance in incident irradiance can influence the energy yield and financial position of a photovoltaic installation in Singapore This whitepaper analyses the level of variance seen over a 15 year period in annual irradiance profiles in Singapore and how this variance will affect the performance of a REC photovoltaic installation and the impact on financial returns under different irradiance conditions. The incident irradiance fluctuation in Singapore will be quantified by Global Horizontal Irradiance (kWh/m²) values while the financial return will be measured by levelized cost of energy (LCOE), payback period and internal rate of return (IRR) for a given solar installation over a 25 year period.