Abstract: A fluid heating apparatus includes a thermally insulated housing divided by a thermally insulated vertical partition into a flue passage and a heat exchange chamber, the partition having top and bottom openings providing communication between the passage and the upper and lower ends of the chamber. A heat exchanger comprising an array of pipes and fins is arranged in the chamber such that an air plenum is provided above the heat exchanger and a firebox is provided below the heat exchanger. The fire box is lined with firebrick and a plurality of electric heating elements are arranged in the firebox. A fan is provided in the housing for circulating air from the flue passage, through the lower opening to the firebox, over the heating elements, up over the heat exchanger to the plenum and through the top opening to the flue passage. Means are provided for circulating fluid to be heated through the pipes of the heat exchanger to a point of use, e.g. the heat exchanger of a residential air heating system.