June's solar generation stats

Here's the graph for June's generation from our array of solar panels. This is for our 2kW 8 panel solar array (Panasonic HIT panels), mounted on our south-facing roof at approximately 35-40° angle from the horizontal.

The dark orange line is June - the light orange line is December by way of comparison.  At a total of 270.6kWh for the month, that's 59.29kWh higher than the forecast.

Here is June included on the yearly chart:

And the yearly sun-strength chart, which is taking shape nicely, showing more of the year:

Since this chart takes account of the total number of hours of sunlight in each month sunrise to sunset  (which doesn't change from year to year), there are only two factors that affect the shape of the graph:

1) The increasing strength of the sun as it gets higher in the sky in summer.
2) Cloud cover.

The changing elevation of the sun in the sky throughout the year creates a smoothly varying rise and fall in the shape of the graph. It also seems reasonable to expect that the amount of monthly cloud cover would decrease steadily as Spring moves towards Summer, causing the average kWh to increase steadily. 

I've double checked the code in my spreadsheet, and it's right - May really did dip like this.  I conclude that May's anomaly must be due to cloud cover - this year on the Fylde coast, there was more cloud cover in May than there was in either April or March, which sounds counter-intuitive, but the numbers point to this being be the case.

Whether this is a one-off, or whether this is normal for the Fylde coast, I won't know until next year....