RAID 1 has more drives running, so you are going to use more power. But, you have to take a look at the application. If the application requires performance, you have to factor in the cost of energy to get the work done. For nearline storage or offline storage, that's where you want to try to reduce power consumption. If the primary concern is performance, RAID 1 uses more power, but it also gets the work done faster, so it's a balancing act.
Check out the entire RAID FAQ guide.
This was first published in November 2007