The IHeat Electric Tankless Water Heater Model S-12 has the capacity of heating 2.3 GPM which is the equivalent to 1 showers (at 1.5 GPM each), and 1 sinks (at 0.75 GPM each) simultaneously, or any combination which equals to 2.3 GPM. The S-12 can handle these applications in the warmer climates of the US which are Florida, Georgia, Louisiana, Texas, Arizona, California, Alabama, and Mississippi. Anything north of these States the Model S-16 can be used for point of use, or 1-application at a time. A good rule of thumb is if you live in the southern states mentioned here the S-12 can power a 1 to 3 bedroom 2 bathroom home, including dishwasher and clothes washer, please keep in mind that tankless water heaters are designed to heat incoming water at a maximum output temperature based on simultaneous use and inlet water temperatures. So if your demand for hot water decreases your output water temperatures will increase, as well as if you live in the colder states this S-12 will heat less volume of water, this will cause the S-12 to be used in Point of Use applications in the colder climates.