Why does power fall so fast with speed?

Flow scales with speed, pressure with speed squared, and power is flow times pressure — so power scales with speed cubed. It is a property of the pump, not a marketing claim.

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What slowing your pool pump down saves

This is the most counter-intuitive saving in the house. Pump power scales roughly with the cube of speed, while water moved scales linearly. Halving the speed and doubling the runtime moves the same water for about a quarter of the energy.

Pump watts at full speedHours a day at full speedReduced speed (% of full)Days in the seasonYour state

What to know

The runtime is increased automatically here to keep water turnover the same, which is the comparison that matters. Slowing down without extending runtime saves more but filters less.
Single-speed pumps cannot do this. A variable-speed replacement is one of the few upgrades that routinely pays back within two seasons at these numbers — run it through the payback calculator.
Most pools are turned over more often than they need. Cutting an hour a day is free money on top of any speed change.

Questions

Why does power fall so fast with speed?: Flow scales with speed, pressure with speed squared, and power is flow times pressure — so power scales with speed cubed. It is a property of the pump, not a marketing claim.

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