I'm from the Northeast so I don't have the pleasure (or the energy cost...) of a long swimming season, and I'm far from an expert on energy usage. However, switching to the variable speed pump for the main pump seems to make a lot of sense. My filter is a DE filter from the mid-1980's that is still going strong, so I'm not an expert there (though it sounds like you have correctly identified it as a "don't fix it if it isn't broke" issue). What is the energy savings if you switch to the variable speed pump, keep the booster pump, and clean less often? Another option could be to get rid of the booster pump (if the increased flow really helps the pump performance, but I'm skeptical on that point!) and switch to a robotic - they draw (IIRC) around 7 amps, but they can clean your pool in 1/3 of the time (correct me if I'm wrong, Dolphin or Aquabot owners), resulting in a net energy savings while you still clean your pool every day. However, you have an initial cost of somewhere around $1K. Do you like how I got that shifted back to pool cleaning