A high efficiency grate and stove heating unit for extracting useful heat from a fire, comprising in combination a low metal enclosure having an expansive top wall constituting a grate proper for supporting fireplace logs and the coals resulting therefrom, together with multiple heat exchangers in the form of fins or plates secured to the top wall and adapted to cradle the logs thereof. Other fins or plates extend downward from the top wall and abut the bottom enclosure wall to constitute a reinforcement means. In one embodiment, the enclosure includes an air inlet port connected with an electric blower for forcing air into the enclosure, together with multiple outlet ports from which the air, now heated, flows. A series of forward protruding nozzles is carried by the enclosure and communicates with the outlet ports to channel the heated air in directions away from the enclosure and its inlet port. Disposed between the blower and the fire area is a heat shield that intercepts radiant heat from the fire, which would otherwise impinge on the blower and cause overheating of the same. The fins or plates extending between the top and bottom walls of the enclosure form a series of internal compartments, and force the circulating air to follow a tortuous or circuitous path. In a preferred embodiment of the invention, the blower simultaneously pressurizes all the compartments, with each of the latter in turn communicating with one of the enclosure's outlet ports. The arrangement is such that due to the large surface areas of the top wall and plates which are in contact with the coals, high heating efficiency is realized by utilizing heat which would otherwise merely go up the chimney. In another embodiment of the invention the forced draft unit is incorporated in a stove, constituting the bottom wall or fire box on which the fuel (logs, coal, charcoal, or any other appropriate combustible substance) rests. Still other embodiments of the invention provide for the use of water as the fluid medium, and show connections to an existing hot water heating system.