‘water heating energy efficiency’ (ηwh) means the ratio between the useful energy in the drinking or sanitary water provided by a combination heater and the energy required for its generation, expressed in %;
„vee soojendamise kasutegur (ηwh)” veesoojendist-kütteseadmest saadava joogi- või olmevee soojendamiseks kasutatava kasuliku energia ja selle saamiseks kasutatava energia suhe protsentides;