Abstract: An electric heater consists of an open mesh net of heat resistant filaments, for example fiberglass filaments, carrying electrically resistive material, for example, carbon black. On either side of the net is a mat of fiberglass reinforcement. The net and the fiberglass reinforcement are impregnated with a cured, thermosetting synthetic resin. In some embodiments a ground layer is also incorporated between layers of the fiberglass mat. The heater is manufactured by assembling the heater, the fiberglass mats and any ground layers, impregnating the mat thus produced and pultruding the impregnated mat to set the resin matrix of the heater.