Another App As A Home-cooked Meal

Mon Apr 27, 2026

I’ve been working on another app as a home-cooked meal. A few years ago we had some solar panels and a battery installed, so I cooked up an app to show the position of the sun, how much energy was coming from the solar panels, how much was going to the battery and how much was coming from the grid.

I wrote it “caveman” style: i.e. by hand, without LLM assistance. Fast forward a few years and we’ve continued the effort to reduce our impact and increase our self-sufficiency, by replacing our gas boiler with an air source heat pump. I wanted to expand the app to include that too.

In the years between creating the dashboard and adding the heat pump, LLMs have turbo-charged software development. Now I can iterate on a small app like this at five times the speed. Taking advantage of that I’ve been on a feature spree, adding:

• Symbols for the hot water and central heating - both of which are driven by the heat pump.
• The current and target hot water temperatures.
• The current and target heating temperatures.
• If we’re importing from the grid, how much each unit is costing.
• If we’re exporting to the grid, how much each unit is earning.
• Lines between symbols that scale with the amount of energy they represent: the more energy, the thicker the line. This is to try and make it clear from a glance where power is coming from and where it’s going to.
• A banner telling us whether it’s a good time to switch on an appliance or not. A “good time” means we could power the appliance without drawing from the grid.

So now it looks like this:

I’ve dialled in a setup that allows for very fast iteration: Conductor, Claude, Xcode previews, lightweight docs for the LLM to follow and Xcode Cloud. With these things in place I can spin up a new Conductor session, ask Claude to implement a feature and then see it reflected in the Xcode previews within a minute or two. I use previews heavily, so I can see how the app will look and behave in common scenarios without having to launch it or hit real APIs.

When I’m happy with the changes I merge to main and soon(ish) Xcode Cloud delivers a new version of the app to our phones through TestFlight.

Incidentally the last “app as a home cooked meal” I made was Home Tide, which I still use every day - as does my family. It’s also rippled out to people around the world, after I released it on the App Store.