If you know a little about LED grow lights, you know that the output wattage the manufacturer gives is never correct. Most 300W lights produce between 120 and 180 watts per hour. Our favorite 300W light is the Advanced Platinum Series P300 Grow Light because it has the highest output wattage of all the lights listed here. Sure, it has the highest price per watt, but it can last for 100,000 hours and cover a 3ft x 2ft grow bed. The Roleadro 5W 300W Grow Light might have the best coverage, but it only produces 124 watts per hour.