Have you actually done the power calculations? 5 4TB drives (for RAID5 16TB array, so you don't have to keep all the Blu Rays safe) have idle AND ACTIVE READ power below 20 watts TOTAL if you buy the right model. So the hard drives draw 175 kwh per year, if they're running/reading 24x7. Of course, you'd have the hard drives spin down when not in use, so the reality is at most 20% of that power (if you stream 5 hours a day, every day) So 35 kwh per year.
Even if the flash drive required no power, that's only 35 kwh per year, or 175 kwh over a five year expected life span. Your power must cost 100x what mine does if you think the flash could pay for itself with power savings.