Introducing Flux, and some thoughts on agentic coding

By Simon Halvdansson | Apr. 2026

I just finished version 1.0 of Flux, an electricity price tracking app for Android, and wanted to put down some words about the development process along with some assorted musings about agentic coding.

Figure: Screenshots from Flux running on a phone.

Since the energy crisis in Europe around 2022, and especially since starting at SINTEF Energy Research, I have been thinking a lot about energy costs and supplies. Consumers can save (mostly marginal amounts) by optimizing their consumption based on the time of day since electricity prices vary.

If you generally enjoy optimizing things, timing the charging of your car with this market can be a fun activity, and evening out demand generally has a positive impact on emissions. I am such a person, but I also take great pleasure in good design and have a hard time putting up with UIs that don't look good. This was the situation for the Android electricity price apps, at least in my opinion, about a year ago when I started work on Flux.

Figure: Various competing electricity price apps for Android.

So the goal was to design and develop a simple solution to this problem, preferably with a homescreen widget.

Development

In these pre-Codex days of early 2025, at least I was still copy-pasting snippets or full files for simplicity from the ChatGPT web UI. I made some sketches of what I wanted the app to look like but all in all integrating with an energy price API and learning about Android widgets made this task a bit too hard without spending a significant amount of time. Once Codex was released multi-file tasks such as Android app development got considerably easier and I was able to get a working prototype relatively easily.

I was initially using hvakosterstrommen.no/ for electricity prices since they have a good website and simple API but I think my prototype app was eventually banned due to excessive usage. After not finding any other good APIs I ended up making my own based on the official ENTSO-E API. That API is very complex and slow so, using Codex, I set up a very simple solution with a GitHub action which updates a JSON file for each country's prices once every hour. Just giving Codex an API key and telling it to curl was a bit of a "feel the AGI" moment for me at least. The result is the ENTSO-E Mirror repository.

Iterating on the app was mainly done using Codex. I've tried out the MCP iteration loop in Android Studio where the LLM can take screenshots and look at logs and it is magical so this is a clear next step, although I haven't looked at how this can be set up inside Codex. Overall, this was a very nice project to get more comfortable with agentic coding and I'm happy with how nice this initial version of the app turned out.