Watts are Joules / second. If you're doing operations that take 1/20 as much power each but you're doing them 20x faster, it takes the same amount of power in Watts. For a better comparison you'd need to measure Watts * seconds for a given task.
Indeed, like how the best CPU reviews don't just report the power consumption but also the energy consumed to do a given benchmark (power integrated in time for a fixed amount of work).
*1/20 as much energy
Joules measure energy, Watts measure power
skavi is right, in context I should have said that each operation takes 1/20 as much energy. The amount of power depends on how often the operations are done.