YA and LTYP outputs should be provided with a related exceedance probability. This gives the right tool to stakeholders involved in PV projects to take the best decision in terms of risk-aversion. A reduction in the uncertainty of the energy yield can lead to higher values for a given exceedance probability and hence a stronger business case. Various efforts in the literature show the importance of having a common framework that can assess the impact of technical risks on the economic performance of a PV project.
The most important parameter influencing the energy yield assessment is the site-specific insolation. Several aspects need to be considered: reliability of the database, inter-annual variability, long-term trends.