They'll make good seed starting lamps but I wouldn't rely on them to give you a meaningful harvest. Remember in addition to light temperature (Kelvin) you also need to make sure you have enough lumens (at least 15000 per square ft just to play the game ). A 400w HPS typically throws 50,000 lumens. A 1000w HPS usually throws around 150,000 lumens. Try and find a replacement bulb online and see what the lumens are. That will tell you how much more lighting you'll need