According to analysts at Citigroup Bank, wind speeds in British wind farms are falling. According to the analysts, this trend has intensified in recent years and is therefore having a negative impact on the profitability of the installed turbines, which were designed for higher wind speeds. Of the companies affected, such as Orsted A/S and SSE Plc, Orsted has issued a profit warning stating that the below-average offshore wind speeds would affect the entire offshore portfolio. SSE Plc. also cited "unfavourable weather conditions" as the reason for the below-average production this year.

The Citigroup experts see "possible signs of climate change" as one of the reasons for the decline in wind speeds. Based on historical wind speed data collected from 170 wind turbines across the UK, they found that wind speeds have "declined" over the last decade, particularly in Scotland. Previously, since the beginning of the millennium, speeds had been "largely unchanged", they write.

Furthermore, outdated plants, inefficient power systems and interference from neighbouring wind farms are cited as possible additional reasons for the decline in energy yield.

According to Citigroup analysts, from an investor's perspective, it seems necessary to reassess the production of renewable energy, its impact on the internal rate of return of a project and, consequently, "its impact on the value creation of the entire company".