EV Solar Charge Planner

We’d bought an electric car and had solar panels installed, and as the Irish summer slowly got going I kept wondering the same thing at bedtime: should I charge the car from the grid tonight, or wait and charge it from the sun tomorrow? It’s a trivial question — not much more than a customised weather forecast focused on solar energy.

Instead of fighting the App Store’s search for a solution, I opened Claude Code on my phone, dictated three paragraphs of requirements, and brushed my teeth. By the time I was getting into bed, it had delivered a mobile-optimised page that pulls open weather data for my location and rates which of the coming days are best for charging from the sun. Ten minutes from “I wonder if…” to “I have the solution” — the story I told in SaaS is dead; long live SaaS!

How it was built

Deliberately the simplest thing that works: a single index.html with vanilla JavaScript and CSS, a service worker for offline/PWA installability, and a manifest. No build step, no framework, no backend — the Open-Meteo API is free and needs no key, so the whole thing hosts for nothing on GitHub Pages. I did not look at the code. I did not source the data. The only user is me and the only requirements are mine.