TL;DR: do you actually need to change?

Some applications (ie databases) will keep as much data in RAM as they can, just for speed…

So, have you got to 80% gradually as you’ve been adding functionality, or has it always been there?

It’s not the route I’ve gone, but lots of people seem to be having success with retired small form factor business machines. Getting a good deal on used business stuff seems to be the key, ideally locally, where they just want to get rid of it compared to ebay. A low-end Intel from 4 years ago is annoyingly good computation per watt.

Also, take your power bill and calculate the cost of a watt for a year. Remember that number for all future purchases. Where I live, it’s around $1.50/watt-year. A 60-watt always-on computer gets pricy quickly.

A slow reply, but I’ve recently migrated from a Pi to an ex-business micro form factor PC. It ended up costing about $150. Whichever one and spec you get, the RAM can be upgraded in most instances to 32GB when required, and most have at least one M2 slot.

Check out ServeTheHome on this. If you go for a fairly recent chip, and pick the t-series (lower power), a box with HomeAssistant running in a VM uses less than 10w at the wall most of the time. Not much more than a Pi, and with far more room for expansion.

I went down the VM/Hypervisor route, and would recommend it. It gives a lot more scope for fixing problems, and you can also use it to host other things as needed.

If you have a college or university near you, search online to see if they have a property disposition department.

I just got an HP Z2 SFF from my local university for $182. It has a Core i7-8700, 16 GB of RAM, and a 512GB NVME SSD.

I run proxmox so I have a VM dedicate to HA OS with frequent backups. This allows me to also run a number of other things without worrying about inadvertently messing up my HA install