Over in your other thread, I see from the pic you posted that you have what appears to be a suction side cleaner.
New Member, New Pool Owner (Livermore, CA)
You may need to run the pump at higher than 1000-1100 rpm to allow the cleaner to do its job. If so, you may want to run the pump at 2500-2900 rpm (as a starting baseline - adjust as needed) for 2 hours in the AM and 1000-1100 rpm in the afternoon. Start out on the low side as far as rpm's and run times. If the cleaner does its job to your satisfaction, you can try decreasing the run time at the higher rpm. Likewise, if the cleaner isn't doing as well as you'd like, maybe increase the AM rpm (in 100 rpm increments) or run the pump in the afternoon for a short period at the same rpm as the AM - during part of the 2 hours afternoon run time. Running at low rpms (1000-1200 rpms) will increase surface skimming effectiveness in most pools. Run at the minimum needed at the higher rpms to allow the cleaner to keep the floor clean. Run the rest of the time at lower rpms to save $$$ on electricity.
So basically, run it long enough to keep the pool clean and free of debris. Another consideration is running the pump (especially at higher rpms) during off peak electric rate times - if it's a consideration to run during lowest rate times.
It's a balancing act. Start out as pooldv suggested (4 hours total run time - 2 AM and 2 PM) and adjust from there to your needs/wants. Keep a written log of the settings and results. This will help you pick the optimum for your pool. If, during certain times of year, you get more surface debris you can increase run time at the lower rpm setting to help skim the stuff off the surface (and reset to your normal run time after the debris issue passes).
As an example of electric usage, my VS pump uses 108 watts/hr at 1100 rpm and around 1600 watts/hr at 2800 rpm. So you can see that running at lower rpms saves a bunch, even if running on low rpms for longer time periods.