ROAST ::

I’ve been adding a display mode to my solar panel analysis program to show the monthly variation in output. It shows the anomaly in percentage terms against the average output for the month. Here are the results for 2012 to May 2025:

Each vertical line represents a month. The very bad result for April 2016 (the line would extend below the graph) is due to the panels being offline for half the month while our roof was replaced. And May 2025 is bad because only the first 10 days are being counted.

It’s interesting to compare this with the following graph, courtesy of the Met Office:

Source:https://www.metoffic … shine-anomaly-graphs
(Select the “Sunshine” option, and “2024” from the drop-down list.)

This shows the sunshine recorded over the whole country for 2024, broken down into regions. Now 2024 was our worst year so far for the panels — it was even worse than 2012, the so-called “year without a summer”.

Look at the 2024 section in the top graph, and note how the only above-average months, coloured orange, were January, June and December. (And even very good results for winter months make very little difference to the yearly figures — we can generate more power in one summer day than the whole of December or January).

Now look at the lower graph, the England results (also in orange). The figures here — remembering they’re for the whole country — are in pretty good agreement, with January and June being the only above-average results in the first half of the year. They disagree about August, which was slightly above average, and December, which was well down for England as a whole. We did better here in Yorkshire, about 9% above average.