2 things to note with the eco2 water heater, the heat exchanger is in the outdoor unit, so in cold climates, you need heat tape and insulation to keep it safe from freezing, also due to heat pump design there are some strict limits when using it for both heating and domestic hot water. This due to the heat pump which is designed for a single pass thru the heat exchanger that is heating cold water to hot water, and not reheating warm water.