Abstract: A portable electrically-powered space heater includes an electrically-powered boiler generating steam at subatmospheric pressure from a mixture of water and ethylene glycol that is circulated through a closed loop heat exchanger, portions of which comprise fin-tube radiators. The boiler is thermostatically controlled by a thermostat located in a chimney into which a downdraft of ambient air is drawn by a fan creating a forced-flow of air over the fin tubes. An automatic temperature-responsive time delay mechanism allows the boiler to get up to its operating temperature before the fan is actuated to draw air across the thermostat. The heater is further characterized by a novel design wherein a pair of upstanding heat exchangers are each housed in branches of a generally Y-shaped housing with a fan located in the stem-forming portion thereof effective to cooperate with the heat exchangers and the double-walled side panels alongside thereof to distribute a curtain of warm air over a 90.degree. or better swath.