Although electric radiators of the past were not designed as light sources, the heat sources were nothing more than carbon filament lamps. These units were quite popular in 1912. The lamps were made in the 250-watt and 500-watt sizes for voltages between 45 and 130 volts. A 250-watt size was also made for voltages between 200 and 250 volts. Fixtures were made that held from two to six lamps. The larger units were more popular abroad than in the United States.