These signs typically contain two or more small, incandescent lamps which use a total of 20 to 50 watts and last from 2,000 to 5,000 hours. An exit light left on 24 hours a day, every day, burns for 8,760 hours a year, so a single sign may use from 175 to 438 kWh of electricity per year. In addition, it requires lamp replacement perhaps four times a year, an added expense and maintenance burden. Exit sign conversion kits are available to replace incandescent lamps with a fluorescent lamp and ballast.
Some fire codes require that a two-lamp backup system be used.
And Furthermore . . .