light bill

Etymology
So called because electricity was once used mainly for lighting; see 1940 citation below.

Noun

 * 1)  An electricity bill.
 * 2) * 1940, C. A. Winder (Director, Division of Engineering and Operations), quoted in: United States. Rural Electrification Administration, Rural Electrification News: A Summary of Rural Electrification Activities (page 26)
 * People who have been connected to utility electric lines have used them almost entirely for lights, because of the expense. But now with plenty of power, calling their monthly statement a light bill is, I believe, wrong psychology. Too many come in and remark about the amount of their light bill even though they may use 50 to 100 kilowatt-hours.