There are many older type exit signs in use today that have both D.C. lamps which are powered by a battery, that operate in the emergency mode when a power failure occurs. However, NFPA 70: National Electrical Code requires exit signs to be illuminated when, either externally or internally, twenty-four hours per day in order to identify a means of egress.
That being said, many exit signs have an A.C. power source which power lamps or a combination of lamps consuming 20-40 watts of A.C. power. These lamps being on a total of nearly 8800 hours per year at 10-15 cents per KwH can cost you as much as $55 per year to operate in addition to the cost of labor and material to replace lamps.
The exit sign LED retrofit kit can save you over $100 per year per sign in your facility. They now offer hard-wire or screw-in type LED replacement kits consuming only 2.8 watts per kit and your return on investment (ROI) is unheard of, at approximately six months (including installation labor). With the estimated LED life expectancy of 100,000 hours you’ll never need to replace an AC lamp again and your investment will payback for many years to come.