Hi - I'm not a self-builder, more a renovator, and I'm not skilled in all departments so I mostly decide what I want and pay others to do the skilled work. I bought a small 1950s house as my "forever home" so I don't have to justify capital outlay (as I'll never see it anyway); I'm more concerned about keeping future running costs as low as possible, as a hedge against a severe drop in income and/or massive rises in prices. So I started by installing solar PV, mostly for hot water via a Sunamp heat store. At some point I'll add a battery as I'm getting far more power each day than I need just for hot water, but I'll wait a bit as the prices are dropping. Next on the list is a heatpump for the central heating, replacing an ageing gas boiler.
The part I'm doing all myself is smart control of heating, only turning on radiators when/where they are needed, on a room by room basis via electric radiator valves driven by wifi relays. Temperature measurement is done by wifi thermometers in each room, and a Rasperry Pi computer looks after the system. Data is sent to and from my website and monitored/controlled through a mobile-friendly web app. By doing it myself I can drastically reduce the hardware cost compared to something like Hive. I've come here in case there are others working on similar ideas I can compare notes with., and also to pick up tips about other things that may be related to the overall project.