Light output is measured in "lumens." A T8, 32-watt fluorescent bulb is engineered to emit up to a generous 95 lumens for each watt of power taken in, according to Other Power. T8 bulbs lose only six percent of their lumen output during the first 40 percent of their rated lives, according to Facilities Net. T8 fluorescent bulbs are some of the longest-lasting bulbs on the lighting market. They are rated to last from 20,000 to 30,000 hours, according to Buildings. Buildings claims T8 bulbs have an excellent color rendering of between 70 and 95 (100 is the highest possible rating).