But with the logic that you should always be supplying lighting fixtures, shouldn't that logic apply to all the electrically operated appliances as well? Or on some commercial industrial you should be supplying specialty electrical appliances, conveyors, lathes, CNC machines, processing and packaging machines......? If you do that, when there is problems or they don't do what customer wanted them to do or as well as they hoped, now it is at least partially your problem. If all you did was supply power to it you don't need to be an expert on everything else about it or provide any kind of warranty on it.