It just depends on how much I make each time. When my plants are mature each DWC bucket holds 2.5gal and I change my solution every 10 days. I can make 4.5 gal each run in my small still and 14 in my large still but my large still runs on propane. It uses 1/5 of a grill tank per run. My small still is electric so it virtually costs nothing. Am I saving money? Probably but I dont know how much. I basically do it because I can, because I can use any water source, and I dont always have the money to run out and buy gallons of water at $1gal everytime I do a nute change. When I use the small still I know im saving a dollar a gallon but it takes several hours to run.
As far as any difference, I don't know if this has anything to do with the water but when I was using local spring water(266ppm alone) my plants wasnt using much nutes but in the past 24hrs my plants have used over 200ppm per plant. The high calcium in my spring water probably was locking up some of my nutes. Calcium is critical in nute absorbtion but too much can cause problems. Happy medium Main, happy medium!