... CE. IEC, ETL , ISO certificate approved 2.High-efficiency, energy-saving 3..-25 degree can work steady 1..(High-efficiency, energy ... %, the average COP is above 4 , even more energy-saving than solar heaters with electric booster heaters. Save bill for ... integrated with such Peripheral control as circulating water, hot water supplying, cold water re-filling and water return back, no need extra electric ...