The UK's Hottest Day Exposed a Hidden Solar Problem
- jontracey4
- 19 hours ago
- 2 min read
When the UK experienced its hottest day of the year, most solar owners were expecting record-breaking generation. After all, more sunshine should mean more electricity... right?
Not necessarily.
During the heatwave I noticed something unusual with my own solar system. Despite clear skies and bright sunshine, my SolarEdge inverter wasn't producing the level of power I expected. At first glance everything appeared normal, but a closer look at the live data in Home Assistant revealed that something wasn't quite right.
Can Solar Panels Get Too Hot?
This is one of the biggest misconceptions about solar energy.
Solar panels need sunlight to generate electricity, but they actually become less efficient as they get hotter. A small reduction in panel efficiency is perfectly normal during very warm weather.
However, in my case, the panels weren't the main issue.
The Hidden Problem
After comparing historical performance and examining my Home Assistant dashboards, I discovered that my inverter appeared to be reducing its output as temperatures increased.
The inverter was effectively protecting itself from excessive heat, quietly limiting power output without generating an obvious fault that most homeowners would ever notice.
If you don't regularly monitor your solar system, you may never realise this is happening.
A Simple Experiment
Rather than guessing, I decided to test a theory.
I placed a cordless Ryobi fan beneath the inverter's heatsink to increase airflow and help remove heat from the unit.
The results were almost immediate.
Within minutes, the inverter temperature began to fall and the power output recovered. Watching the live Home Assistant graphs made it very easy to see the relationship between cooling the inverter and restoring performance.
It wasn't a scientific laboratory test, but it was convincing enough that I'll now be looking at a more permanent automated cooling solution.
Could Your Solar System Be Doing the Same?
If you have:
A SolarEdge inverter
Another brand of string inverter
Battery storage
Home Assistant or detailed monitoring
it's worth reviewing your generation during periods of very hot weather.
Most systems are designed to protect themselves, so reducing output isn't a fault—it's often intentional. The important question is whether your inverter has sufficient ventilation to avoid reaching those temperature limits in the first place.
Watch the Full Investigation
In my latest YouTube video I walk through the entire investigation, showing the live Home Assistant dashboards, the data that first alerted me to the issue, and the surprisingly simple cooling test that restored performance.
If you've ever wondered whether hot weather could actually reduce your solar generation, or you're looking for ways to maximise the performance of your solar panels and inverter during a UK heatwave, I think you'll find the results fascinating.
👉 Watch the full video here: https://youtu.be/3OnCUvhlTWg
If you enjoy practical, data-driven videos covering solar panels, battery storage, Home Assistant, heat pumps and UK energy tariffs, don't forget to subscribe to the channel so you don't miss future experiments and real-world testing.
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