Is that twice the power at full bandwidth? Because if so, then the SSD is still more efficient, because those reads/writes will be over a lot more than twice as fast, and the SSD can go back to idling.
I guess that is active power usage, but considering how much faster SSD's are compared to HDD's I doubt that scales with amount transferred (esp for random read/writes). So what would the power usage be when the total over active work time is counted?
Samsung quotes 148 MB/s per watt for the PM1643, for sequential transfers. Hard drive performance tops out around 270 MB/s and draws something less than ~9.5W, so the SSD is 3-5x more efficient for sequential transfers. For random IO, it's several orders of magnitude difference in performance and efficiency.
The most power-efficient consumer SSDs are an order of magnitude more efficient for sequential transfers than the Samsung PM1643. Eg: https://www.anandtech.com/bench/SSD18/2460
The PM1643 16TB SSD is about 7 times as expensive as 16TB disks. (2600 vs 360, euro)
The PM1643 actually uses more than twice as much power in use (r or w) than a spinning disk. Idling they use the same 5W.