HPS is short for high pressure sodium. They are used by gardeners to increase the amount of sunlight in a day and to supplement for natural sunlight in places that do not have enough sunlight in order for plants to survive. HPS grow lights provide more red and yellow colors. The light can be used throughout the plants growth cycle. They are used best with metal halide lights. The lights are used with a reflector. This is done to heighten and check the light provided and includes an electric ballast to contain the electrical current in the light. One of the drawbacks of using high pressure sodium lights is the lack of blue light. This light dictates a form of supplemental lighting during other growth phases when natural sunlight is unavailable. This issue dictates the use of the LED light which produces the blue light. The blue light helps the growth and vegetation process which gives it an advantage. Another advantage is that LED grow lights replaces ballasts whereas the hps grow lights require it.