Select models are assembled with our very own patented self-modulating technology so they regulate exactly how much energy is needed to heat the amount of hot water needed. The Eco 18 is capable of heating two sinks and two showers simultaneously in warm climates, and a shower and sink simultaneously in colder climes. When sized correctly your tankless water heater will provide you with endless on-demand warm water. It heats water as it passes through the unit, instead of storing hot - saving you up to 50% n the Eco 11 is designed to heat up to 2 gallons per minute and is optimal for the weather of 67 F and above. Without the correct electrical infrastructure, your unit may not fit onto your breaker panel, according to the manufacturer's specs and wiring diagram on cnn.com/eco-smart-water-heating-systems-assembly-equipment-diagnosis.