I’m on the Octopus Agile electricity tariff, where the price changes every half hour based on wholesale costs. This is great for saving money and using less carbon intensive energy, provided you can shift your heavy usage to cheaper times. With a family that insists on eating at a normal hour, that mostly means scheduling the dishwasher and washing machine.

The snag was not having an easy way to see upcoming prices on my Linux laptop. To scratch that itch, I built a small GTK app: Octopus Agile Energy. You can use it yourself if you’re in the UK and have this electricity tarriff. Either install it directly from Flathub or download the source code and ‘press play’ in GNOME Builder. The app is heavily inspired by the excellent Octopus Compare for mobile but I stripped the concept back to a single job: what’s the price now and for the next 24 hours? This felt right for a simple desktop utility and was achievable with a bit of JSON parsing and some hand waving.

I wrote a good chunk of the Python for it with the gemini-cli, which was a pleasant surprise. My workflow was running Gemini in a Toolbx container, building on my Silverblue desktop with GNOME Builder, and manually feeding back any errors. I kept myself in the loop, taking my own screenshots of visual issues rather than letting the model run completely free and using integrations like gnome-mcp-server to inspect itself.

It’s genuinely fun to make apps with GTK 4, libadwaita, and Python. The modern stack has a much lower barrier to entry than the GTK-based frameworks I’ve worked on in the past. And while I have my reservations about cloud-hosted AI, using this kind of technology feels like a step towards giving users more control over their computing, not less. Of course, the 25 years of experience I have in software development helped bridge the gap between a semi-working prototype that only served one specific pricing configuration, didn’t cache anything and was constantly re-rendering; and an actual app. The AI isn’t quite there yet at all, but the potential is there and a locally hosted system by and for the free software ecosystem would be super handy.

I hope the app is useful. Whilst I may well make some tweaks or changes this does exactly what I want and I’d encourage anyone interested to fork the code and build something that makes them happy.