The RH360 solar reheat kit provides efficient, consistent tankless backup for solar water heating. Previous other solar tankless backup solutions fed the hot line from the solar tank directly to the tankless backup unit, which would heat water when the temperature started to drop, which could lead to temperature fluctuations, the firm says. The RH360 kicks in only when the water temperature in the solar storage tank drops below a pre-set point, drawing the coldest water from the bottom of the solar storage tank to the tankless unit and returning it to the top of the tank, helping to maintain consistent-temperature hot water delivery, the maker says; minimal tank mixing allows for optimization of solar gain, and the elimination of off-cycle thermal circulation decreases heat loss. 866.746.6241. www.rinnai.us.