I use a 1hp chiller, 2 6" ice boxes, 2 res coils, and water cool my co2 gen. The 1hp is minimum to run a normal 1200w room. Mine works hard. The most important thing is to keep the room with the chiller in it at a reasonable temp. All the heat from your room and the added heat from the chiller itself will be dumped into that room. This is overlooked usually by most first time water cooler guys and it is the most important aspect.