Originally Posted by Richard

You want to supply a total 55W to 75W per square foot of broadcast light to the plants, in the 6500K color temperature. The soft white bulbs are not the right color temperature, but check the label on the daylight CFL's. Typically the most effective way to do this is with the 4-ft long TF HO 6500K bulbs.

As an example, if you are going to be broadcasting light downwards from hooded fixture(s) that have an 6-ft by 6-ft "footprint" on the floor, then you'll want a total of 1980 to 2700 Watts of power. Direct sunshine through a window at your latitude can supply about a 1/3 of that. Windows reflect back a significant amount of power in the visual spectrum, and since the light is not coming overhead on all sides of the plant, you only get a fraction of what you would outdoors. Rotating the plant will not help. You'll actually make it work harder by having to process input on one side one time, another side another time, etc.

The power rating should be actual power, not "power equivalent in luminescence". So for example, a 23W bulb with the "brightness equivalence" of a 100W bulb, is only giving you 23W of power.