A high-efficiency boiler or HR boiler is a gas heating boiler that has a higher efficiency compared to a conventional gas boiler, resulting in lower gas consumption. The Gaskeur HR label divides HR boilers into three categories: HR 100, with an efficiency of at least 100%, HR 104 and finally HR 107, with an efficiency of at least 107%. The high efficiency is achieved by preheating the cold return water in a heat exchanger with the flue gases.
