This bulb replaced a 150 watt fluorescent bulb that had lost most of its brightness and seemed to need to be warmed up before it peaked. Simply screwed into the socket and switched on immediately. It was much brighter than the 150w fluorescent it replaced. I asked my son to check it out after installing it and left the garage door to the house open. When he came out of the house he asked if I left the large exterior garage door (there are no windows) open because he thought sunlight was streaming into the house from the garage. Entering the garage, he was surprised to find that the large exterior garage door was closed. Well I've only had it a few weeks so I can't vouch for how long it will last. What I can tell is what we needed for our garage.