why power is lower if memory accesses are spread over a longer time?

I am studying Intel speed shift, I saw a sentence:

"If these memory accesses are spread over a longer time, the power is lower but the energy is equal"

My understanding is that when longer runtime, we need more energy even platform power is constant.

I think power = V x I at a testing moment.

Why power became lower if memory accesses are spread over a longer time ?

ref: http://webee.technion.ac.il/~ran/papers/IEEE-Computer-H-EARtH-2016.pdf

page.35,

"Fixed energy (not shown in Figure 2): During workload execution, a fixed amount of data is transferred to and from memory, disk drives, and so on. This activity is a function of the application footprint and the devices’ physical characteristics; it does not depend on CPU frequency and therefore translates to fixed energy. If these memory accesses are spread over a longer time, the power is lower but the energy is equal"