Wattage is less than a 2.5" laptop hard drive usually, unless very active (unlikely to happen for long periods of time) and especially if very active and a high end PCI-express m.2 or straight PCI-express SSD.
But usually when going full blast with writing, still less power than a laptop hard drive being 100% busy.
When not doing much, hardly consumes any power at all (less than a watt).
Once you go SSD, you don't go back. 540MB/s is plenty for a desktop/laptop in most cases except extreme uses.