Hi mano verde,

I ain't no expert here but the guy I just bought my MH light kit off of said you will need 400W - 1000W to grow tomatoe to fruit. I'm sure others will add input based on experience but I think you might want to start preparing yourself to spend a few extra dollars.

Best of luck,

Bill

Well you won't need 1000W for a single plant, but 20W is not really enough. Can you not find a sunny window even in the middle of summer? Tomatoes are notoriously difficult to grow with artificial lights because they are so tall and a common solution is just to use massive amounts of light.

Although typically 30W of light is plenty for a square foot of plants such as a single tomato, a tomato plant should really be considered more like five square feet since that is the area from the side. Even the most creative solution is going to need 100W of light or more, and so you should be looking at a couple of 4' fluorescent tubes mounted on each side of the plant, maybe four tubes if you want two or three plants. Remember that something like this will cost something like $10/month to run for maybe 16 hours a day, plus any extra load on your A/C from the heat, so it doesn't pay to try and use cheap but inefficient 20W compact fluorescents.

And don't get an aquarium light, they are for ... well ... aquariums! Get cool white fluorescents, or daylights, or plant lights, but not something that is designed to make coral glow in the dark :)