According to the Met Office, yesterday saw the hottest July day on record in the UK, with temperatures hitting a scorching 36.7C (98F) in some parts of the UK.

Indeed, by 8am here in sunny Gloucester, the mercury had already climbed to a staggering 25C.

Thanks to a southerly wind, warm air has been wafting its way up from the Continent, bringing with it scorching temperatures and clear blue skies.

Indeed, the last few days have been absolutely glorious and provided us with a welcome break from the mixed bag of mediocre weather we have been ‘enjoying’ since the wet and miserable arrival of May.

We’re experiencing a bit of a change today, thanks to frontal systems pushing their way in from the Atlantic, bringing thundery showers and a dramatic drop in temperature.

But worry not, things are set to heat up again tomorrow.

During the past few days of blazing sun, we have been receiving calls into the Roxon office from customers asking why the output from their solar PV panels is down, even though there is bright sun beaming down on their roofs.

A perfectly logical question – surely, more sun equals more solar generation? Well, ironically, that’s not actually the case.

You see, unlike solar thermal systems, which depend on the sun’s heat to do their work, solar PV works on light. So, despite relying on the sun to generate electricity, solar panels actually like to stay as cool as possible. Indeed, temperature is one of the important factors affecting how much electricity your panels will produce. It’s ironic – but the more sunshine you get, the hotter the panels get, and this in turns counteracts the benefit of the sun. This has to be the ultimate paradox, surely?

You may have noticed that your solar PV produces as much output on a clear, sunny winter’s day as it does in the summer – even though the sun is lower in winter.

The reason for this is because your solar PV panels are far colder – maybe almost zero degrees – which actually improves their efficiency.

So, on a hot day in Summer, the amount of electricity your panels generate could be a few watts lower than your normal daily output when temperatures are below 25C.

Conversely, on a sunny day in Spring, Autumn, or even Winter – when temperatures are lower than 25C – the amount of electricity produced would actually increase above the maximum rated level.

So, if you noticed a slight decline in your panels’ output when the heatwave struck this week, don’t worry, you haven’t got a failing module. Your system’s in fine working order and will perk up again when the temperatures return to normal levels for a typical British ‘summer’.

To find out more how solar PV works, check out our fact sheet here.