I built the tool I wish I'd had

Solar has been a big part of my life as a home owner. But it wasn't until I moved into a house with someone else's system that I realised how little most owners can actually tell about their own.

At one house I installed the system myself. I picked the panels, ran the numbers and watched it every day. I knew what a good day looked like, I knew what a cloudy one cost me, and I was confident it was pulling its weight.

Then I moved into a house where the solar came with the roof. There was no app, no paperwork and no installer to call. I didn't know how big the system was, how old it was, or whether it had ever been checked.

All I had was a small screen on the inverter in the garage, showing a number.

Was it a great day or a terrible one? Were the panels dirty? Was the inverter tired? Was something broken that had been quietly costing me money for years? A number on its own means nothing without knowing what the sun actually did that day.

So I built “Is My Solar Working?” You enter what your system made, along with your postcode, and it checks that against the real sunshine where you live. In a few seconds you get a straight answer about whether your system is doing its job.

It's free and there's no sign-up. It's for anyone who has stood in front of an inverter screen and wondered the same thing I did.