Abstract :
Lighting one room with a 100-watt incandescent lamp for 300 hours, which is about the average burning time of a lamp a year, costs $2.40 or less. Lighting another room of the same size, the same length of time and with the same brightness, using the original lamps made by Thomas A. Edison 50 years ago, would now cost more than $20.00. At then existing rates for electric service the cost would have been much greater.
