Watts dont matter its lumens that are most important, and for three plants in flowering stage you will prob need over 10,000 lumens if you want to get a decent harvest.. cfls emit less heat and use less watts than normal incadesent lights consiquently using less electricity but dont emit much lumens unless you have plenty of them, HPS are very efficient at emitting lumens but also emit a great deal of heat making you worry about making your grow area,grow box,whatever cooler because of all the heat.