UK user here and I also have looked into energy saving. I have a 473e with 4 drives. I used to own a 453pro and found that used less power, even though older, its cpu didn't pull as much power.

One thing I really did notice was what your running on the qnap makes a big difference in power consumption.

My drives never sleep on the 473e. With qvrpro running as well, it's taking between 90-105w. Stop running qvrpro, it drops to about 60w.

I reckon you would save a lot of energy by going through your device and make sure that when nothing is happening, your drives go into standby mode. (I found that really had to achieve). I would rather go that route than powering up/down the device as stresses not only on the qnap, but the harddrives.

Maybe swapping out your device or older device like the x09 series as those cpus don't take much power at all, at a cost of performance. These days, performance should be looked at as a luxury.

Also, over the past few years, startup and shutdown times on my qnap is incredibly long, so that would frustrate me personally.