When used properly, CFL lighting provides an estimated 0.3 grams per watt. Compared to the 1 gram per watt that HPS provides it just doesn't stack up. The good in it though is that they use less energy and don't get too hot unless you have a very strong CFL (usually the ones that need their own ballast). However, despite what most people say, YOU CAN GROW A PLANT TO HARVEST FROM ONLY CFL. It's true. So if you are serious about what you are doing, you might as well get an HPS unit. If it's just a one time thing or an experiment, then go ahead and use only CFL. Goodluck.