My experience matches David's. The Intelliflow shows you GPM, RPM, and Wattage. The GPM is clearly close to reality as I can tell by how fast it fills an empty spa and how fast it runs a cleaner. As the system runs its test of your pool, it clearly is much more efficient up to a certain speed. Above that it takes progressively a lot more wattage to move a lot less water. Mine behaves differently than my neighbor with the same pump and larger plumbing. Mine takes almost double the power to move 20GPM as it does to move 15GPM. It does clean the pool a bit faster at 20GPM but it is much cheaper to run it a bit longer at 15GPM. My neighbors pool takes only 35% more to run 20GPM than 15GPM. This is almost exactly what you would expect if the system flows freely, 33% more water flow for slightly more than 33% more power.

You can tell how dirty the filter is by how much wattage is required for it to move 15GPM of water.