Well the rule of thumb is 30-40watt for vegeing plants and 50watts per foot square foot obliviously sativa will take more light as it gets bigger and how big you grow, if you can them to no more than two half out one gallon pots, you should be able to do go with 40-50watts per square foot,,if you grow to plants to over the 3 feet 3-5 gallon bucket you may wish to use at least a 600 watt grow light or lamp..I have look at the HID lights they have yet to compare to what HID lamp/light can do.