Whats method of hot water recirculation is the most energy efficient?  It seems we waste a lot running the water faucets until it gets hot.  Some of my friends say gravity return, others say recirc pump.  I know it needs pipe insulation, but eventually the water inside will cool off also.

I have a 2-floor home with basement.  The 50-Gal. gas water heater in the basement is on the South end, the pipes go to the North 14 feet below the 1st and 2nd floor baths, then 18 feet more to the laundry below and kitchen sink/dishwasher above.  I suspect I will need 2 return lines, one from 2nd fl. bath, other from kitchen sink.