So I have a micro, single plant grow in an old computer case. I read that you need a 6500k light and 3000 lumens for one plant. I found a 42 watt light in order to keep the PC relatively cool, and it's a 6500k, but it only outputs 2800 lumens. For a single plant, should this be enough? Thanks for all the help guys.
you'll be wanting more light than that, really. A good rule of thumb for cfl grows is 100w for a single plant and 50w for each extra plant. Make sure its actual watts and not "equivalent". Have a look at other pc grows and checkout their lighting set ups.
You want more then one if you use that light. That is measured in output without the amount of space that you will have your plants away from the light. Remember that the further the light is away from the plant the less actual light it is getting due to decrease in light strength at further distances. You may at least 4 or more of these types of lights for your plant at a safe distance away for a good grow. Because your plant will need to take in as much light as it can for food.
How about two of these inside a (rough estimate here) 4 x .5 x 2.5? Amazon.com: GE 89095 Energy Smart 26-Watt Daylight Spiral Compact Fluorescent Bulb: Home Improvement it has a total output of 3220 lumens, along with total replacement of 200 watts.