Energy-Efficient Unraid Server

You can easily track your server’s power consumption with a UPS. The power load can be viewed via the Dashboard tab of the Unraid webGUI. 

For the purpose of creating a power-efficient homelab, ignore the TDP numbers on hardware specs: Low idle server wattage is what you'll want to focus on. See the Hardwareluxx sheet below for help.

Hardware that is more than 8-10+ years old may be cheaper now, but due to power inefficiencies, it will likely be more expensive to run in the long run. Example: Older CPUs run at a much higher wattage at idle.

Most modern PSUs don't run very efficiently at lower loads so consider something like the Corsair RM550x PSU or look into potentially using a PicoPSU combined with a laptop power brick, if applicable to your server specs and use case.

There are power tradeoffs when choosing between 5400 rpm vs 7200 rpm hard drives. Generally speaking, 5400 rpm drives tend to have lower energy consumption and a longer lifespan. 7200 rpm hard drives will also run louder and hotter.

If you decide to spin down, your hard drive power consumption can go down from 3-8 watts idle on average to 0.4 watts (per hard drive) so depending on how large your Array is, you might see large power efficiency gains when spinning down.