I grow indoors in a square meter size space. I want to try using an LED light. What wattage light would I need to get great results? Also, how high should I hang the light(s) above the plants?
I understand your frustration. LED grow lights are still a fairly new product and there is very little info readily available. To have decent results in a square meter space (10.75 square feet), I would go with at least 180 watts. Your plants will do fine with 90 watts for the vegetative cycle, but once they start flowering 180 watts will be required to foster excellent bud growth. The best overhead spacing would be about 35.5 centimeters (14 inches) for the vegetative cycle and 15.25 centimeters (six inches) for the floral cycle.
If you’re willing to spend the cash, then investing in a 350 watt source would produce fantastic results and allow you to expand to a larger 1.3 square meter (16 square feet) space. The overhead spacing should be about 51 centimeters (20 inches) for the vegetative cycle and 35.5 centimeters (14 inches) for the floral cycle. I rounded all the spacing numbers off to make things simpler, but this should serve as a good starter guide.
I hope this sheds some light on your illumination problem.