The pump is the equipment that circulates the pool water. The pump is 100% in control of circulation; it can be analogized to the human heart and its role in circulating blood to the entire body. Traditional pool pumps are based on horsepower. Future pumps will not be; a variable speed pump is the future of pool pumps. With a variable speed pump, there is no more discussion or explanations required for "horsepower" and no more need to decide which pump (in terms of its horsepower) would work best with your pool, given its gallons, plumbing specifications, and filter. A variable speed pump will work with any pool as any speed (multiple speeds) can be programmed based on your pool size and specifications.
While a variable speed pump is somewhat expensive upfront, the upfront cost must be viewed as an investment versus an expense; it would not take long at all to generate a return on your investment due to the monthly energy savings. The variable speed pumps are truly energy-efficient, as they operate at the minimum speed required to perform a given task. A variable speed pump will save you considerable money each month; it truly is the most economical and energy-efficient pool pump available.
With the exception of the overall HVAC system to heat and cool your house, the next highest use of energy is alone attributed to the pool pump (for those of you still using a horsepower-driven pump); this will not be the case with a variable speed pump.
The variable speed pumps are programmable, user-friendly, and completely energy-efficient.
You can read the Pool Manual for additional information about variable speed pumps and all of their features and programs as well as troubleshooting techniques.