The warranty must be at least two years for residential applications and some manufacturers offer longer warranties. Since ENERGY STAR qualified CFLs can also be used in commercial applications like hotels, restaurants, office buildings where the lights are on for longer periods of time, ENERGY STAR requires manufacturers to offer at least a one-year warranty for commercial applications. If you have additional questions or concerns about your ENERGY STAR qualified CFL, please e-mail us at cfl@energystar.gov.