Choose the right size MH/HPS light for your space !
MH/HPS is a great choice for growing green plants! This type of grow light has been the “golden standard” of indoor growing for decades because they work so well at delivering fast growth, big yields and dense, potent buds! They are easy to use and there’s an abundance of information, guidance and other types of help for MH/HPS growers.
Green plants growing under the yellow light of an HPS - HPS grow lights give the best yields of all grow lights!
MH stands for "Metal Halide" and HPS stands for "High Pressure Sodium." These are two specialized types of bulbs that are great for growing plants, from a class of lights known as HID (High Intensity Discharge).
Metal Halide Grow Lights (MH) give off a wonderful light spectrum for vegetative stage High Pressure Sodium Grow Lights (HPS) are the golden standard for growing green plants.
MH lights appear blue and are often used in the plant's vegetative stage (first stage of life). HPS lights appear yellow and are often used for the flowering stage (second stage of life). Either type of bulb can be used for the entire plant's life span, but HPS bulbs are better for the flowering stage. Many grow light ballasts allow you to use both MH and HPS in the same hood/reflector - just take one bulb out and plug in the other bulb - you're good to go!
Choose the right size MH/HPS light for your space
Coverage Area: 2' x 2' (0.6m x 0.6m)
How Far From Plants? Keep 7+ inches (17cm) away from tops of plants
Notes: Nearly all 150W MH/HPS have a “Built-In Ballast,” which means everything is actually attached together and you just plug the light directly into the wall. A 150W does not get very hot compared to all other HID grow lights, and many growers may not need any kind of exhaust system with a 150W.
Coverage Area: 2' x 2' (0.6m x 0.6m) up to 2.5' x 2.5' (0.8m x 0.8m)
How Far From Plants? Keep 10+ inches (25cm) away from tops of plants
Notes: Some (but not all) 250W MH/HPS have a “Built-In Ballast,” which means everything is actually attached together and you just plug the light directly into the wall. Some 250W HPS lights have a traditional ballast, which means that the ballast is a separate piece from the hood. In general, it's better to get a light with a separate ballast if you can - they are more efficient, cooler, and spread their light over a bigger area.
Coverage Area: 3' x 3' (0.9m x 0.9m) up to 3.5' x 3.5' (1m x 1m)
How Far From Plants? Keep 12+ inches (30cm) away from tops of plants
Notes: 400W is one of the two most popular sizes for small-scale growers (along with 600W). A 400W grow light runs relatively cool compared to most other HID lights, but packs quite a punch when it comes to yields. Generally it’s a good idea to set up an exhaust for a 400W grow light to manage temperatures.
Coverage Area: 3.5' x 3.5' (1m x 1m) up to 4' x 4' (1.2m x 1.2m)
How Far From Plants? Keep 16+ inches (40cm) away from tops of plants
Notes: 600W is one of the most popular sizes for small-scale growers (along with 400W). A 600W grow light is the most efficient of all HID lights, which means it produces the most amount of light per watt of electricity. To prevent heat problems, I would not recommend getting a 600W light for a regular grow room without installing an exhaust setup or some other way to control temperature.
Coverage Area: 4' x 4' (1.2m x 1.2m) up to 5' x 5' (1.5m x 1.5m).
How Far From Plants? Keep 21+ inches (53cm) away from tops of plants
Note: 1000W is the biggest standard HID grow light size. A 1000W grow light is extremely powerful but can also get very hot. To prevent heat problems (which can adversely affect your plants), it is important to set up an exhaust setup or some other way to control temperature.