The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute has developed a free, easy-to-use online tool that will assist growers to evaluate the performance, efficiency, and economics of a wide variety of horticultural luminaires, typically used in greenhouses and other controlled agricultural environments. This online tool called the horticulture luminaire calculator allows growers to accurately compare several luminaires and select the one that will be most effective for their particular application.