Pre-SSD days I wondered the same thing so I purchase a power/watt meter to check my 6 disk RedHat LVM RAID-5 arrays...it was eye opening.
Electrical consumption alone, not even factoring in my stress "is it working", man-hours, backups, user/family training, UPS units, or drive/cassis hardware costs it was clearly cheaper to outsource storage.
take a look at Cockpit