Solar PV – 2020 Sunshine Levels

Once a quarter I log my Solar PV reading with my electricity supplier. I have a 3.8 KWh installation on a near-enough south-facing roof in the UK. Along with a Tesla Power2 it generates about 75% of our electricity in any year.

I’ve been doing this for 8 years, and logging the detailed info for the past six. It’s been interesting in that my perception of what makes a sunny quarter often isn’t reflected in the readings. They’ve been reasonably consistent.

1. March-May 2014-19

March-May totals 2014-2019 have been, on average, 1,178 KWh, varying from as low as 90% (1,064 KWh) of that average in 2018 to 106% (1,218 KWh) in 2015. (Graph 1.)

2. Cumulative Total

To show personal perceptions of how much sunshine there is can be wrong, the annual total generation for the past few years is pretty much a straight line. (Graph 2.)

But wow, that’s over 30MWh generated!

I’ve just logged this year’s Mar-May reading. Graph 3 shows what that first graph looks like with that reading added in. The new reading that is an extraordinary 129% above the previous six year’s average, at 1,515 KWh.

3. March-May 2014-20

One rule with SolarPV is the longer the days and the sunnier the days, the more electricity is generated. While a clear winter’s day can hit peak generation it will only do it for a short period because the days are short.

It’s been a very sunny quarter. Based on my generation records, there’s been more sunshine in this March-May than in any June-August quarter since 2014 (The highest was 1,490 KWh in 2018). In every other year June-August has always been the highest generating quarter of the year.

Great for us, in the last three months we used an insignificant 28KW from the mains grid, but I’m really wondering why there’s such a big jump. Was it the Covid19 lockdown giving clear skies, or climate change, or a bit of both? I’m wondering what next quarter will be like, and next year too.

Wet winters, dry clear springs and summers seems to be the new normal here. The weather’s beautiful but I can’t help but worry this is bad news.


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