Using a 150gpd system provides 6.25 gallons per hour. After MACNA 2012, I had a 300gpd system on hand and decided to use it as well. Running the two systems side by side speeds up water production significantly, at a rate approaching 19 gallons per hour. I ran it like this for about a year or so, then reverted back to a single 150gpd system. Eventually, I decided to change out the membrane for a 100gpd instead due to the better 98% rejection rating which helped waste less DI resin over time.