Several householders have asked whether the performance of their PV system indicates problems with their solar panels. The recent electrical output from their roof has been well below expectations. If the output from my panels is any guide, the problem lies in the cloudiness of the last year, and not the system itself. I’ve recorded the output figures from my PV system each month for the last nine years and this annual period has been by far the worst on record.

In ten out of the last 12 months, my panels have produced less than average output for the month. March’s output was strikingly low: 68% of the average figure for the month.

The last year’s electricity production was 90% of the nine year average. Our (badly oriented) 2 kW system produced less than 1,300 kWh, compared to the norm of around 1,430 kWh. You’d expect some small degradation in performance as the panels age but the last twelve months have been unusually cloudy.

The graph records annual output from our PV system over the last nine years with kilowatt hours on the vertical axis.