First, a quick aside. It is not the goal to provide one turnover per day. A typical pool need about half of that. That doesn't relate to your main question, but I needed to mention that.
Over simplifying a little, energy usage is a function of two main factors, resistance to flow in the plumbing, and the efficiency of the motor. The more resistance to flow caused by the plumbing, the more energy you need to use to push the water through. Similarly, the more efficient the motor, the less energy you need to use. One of the main contributions to resistance to flow is the flow rate. Pushing more water through the same pipe means more resistance to flow.
As it happens, running a standard two speed motor on low speed moves exactly half as many gallons per minute, and requires 1/8th the energy. However, the motor also gets less efficient at the same time, so in practice the actual energy usage is about 1/4 as much per unit time. Since it moves half as much water, you need to run the pump twice as long, so the total energy usage is right around 1/2 of what it would be to move the same amount of water on high speed.
With a variable speed pump, this effect gets larger. You can run at even lower speeds and save even more money, getting the cost down to as low as 1/8 the cost on high speed (under ideal circumstances, in practice not quite that good). However, the big savings come at the beginning, so variable speed pumps don't always pay back the additional up front investment (depending on how much more they cost).