HPS stands for High Pressure Sodium, this is a type of HID bulb that uses sodium and is considered the gold standard of grow lights. These bulbs generally come in 150w, 250w, 400w, 600w and 1000w versions and must be paired with a ballast that matches the wattage. HPS lights provide a full spectrum of light, but have an emphasis on the red end of this spectrum. They can be used for the entire life cycle of a cannabis plant, but many growers argue that the extra red light makes HPS lights optimal for the flowering phase.
HPS lights are considered to be the ideal lights for growing cannabis for several reasons. They are relatively affordable and easy to use for the everyday grower, and perform very well. Despite several drawbacks, it is hard to beat the performance of HPS lights. Whenever new grow lights for indoor marijuana are developed, they are usually judged on how well they compare to HPS lights with a similar wattage.
The downside to using HPS grow lights is their efficiency, the main problem is usually the heat generated by both the ballast and the light. With temperatures exceeding 400°C, this system does not use energy very efficiently. The penetration of these lights also diminishes very rapidly and can drop by almost 90% at distance of only one meter. These inefficiencies have caused the European Union to ban the production of High Pressure Sodium grow lights and stimulate the transition to more environment-friendly alternatives like LED lights.
It is important to note that HID bulbs classically only connect at one side, but more modern grow lights use double-ended bulbs. These double-ended bulbs connect at both sides and are up to 30% more efficient than regular bulbs. Double-ended bulbs are simply better than single-ended bulbs, but this is also reflected in the price.
In short, HPS lights are definitely very good for growing cannabis. However, the amount of power consumed can become expensive and unfortunately much of this energy is wasted as heat and sound.