What is The Best HPS Bulb for Flowering?

When you decide to change your light schedule and put your plants into the flowering stage there are many options you can choose from for lighting, however I vastly prefer HPS Bulbs. Luckily HPS Bulbs are very common and are fairly standardized giving you many different suppliers to choose from. In this guide I will provide tips and tricks for choosing the best HPS bulb for flowering.


  • Excellent light spectrum and intensity: One of the biggest benefits is the massive amount of light these bulbs will produce. This will ensure you are getting the most amount of light energy reaching your plants resulting in a better yield. The light spectrum these bulbs output will work perfectly during the flowering stage.
  • Replaceable: The great thing about HPS bulbs is that it will use the same light fixture as a MH bulb. This means you only have to purchase one light fixture and you can just swap out the bulbs when needed. If you have an LED fixture and the lights burn out, you must replace the entire fixture. In the long run this will save you money


  • Heat: One of the biggest difference between HPS and LED is the heat output. LED fixtures put out little to no heat, on the other hand High Pressure Sodium ( HPS ) will create a LOT of heat. If you decide to go with the high pressure sodium make sure you have an adequate ventilation system to control the heat in your grow tent.
  • Higher Wattage: This could technically be a Pro or a Con depending how you look at it. A higher wattage is great because it creates more light output, however this also means higher electricity costs.

Choosing the Best HPS Bulb for Flowering

For most people, once they choose their grow light they generally use it for as long as possible. Although the bulbs may need to be replaced occasionaly, the fixture should last a very long time. The fixture can be broken down into a few parts.

Fixture or Shell: This is the housing for your lights and is usually made of a thin metal. When looking for a HID light I recommend buying one that a reflective material on this inside, as well as a glass cover. The refelcting material helps increase light coverage, and the glass will keep the heat inside the fixture which can later be vented out. I also reccomend using a light fixture that has a glass cover on it. This helps keep the heat inside the fixture which can then be vented away later. you will notice the light fixture has holes on each side to accept the ducting from your ventilation system.

Ballast: Your ballast should have the same rating as your HPS Bulb. For example, if you select a 600W bulb, you must also use a 600W Ballast. Most ballast will come in standard sizes making into easier to match up with your chosen bulb size. ( Standard sizes: 150W, 250W, 400W, 600W and 1000W ). I personally use a 600W ballast for my 4×4 grow tent. I will post some pictures of my set up below.

HPS BULB: The bulb is fairly easy to select. You simply need to choose a bulb with enough wattage to cover your grow area. See the chart below.

Ballast SizeTent Size
150W2’x2′ Grow Tent with 2 plants.
250W2’x2′ Grow Tent with 2 plants. ( recommended over 150w)
400W3’x3′ Grow Tent
600W3.5’x3.5′ up to 4’x4′. This is my personal recommendation for a 4×4 tent.
1000W4’x4′, 5’x5′ or bigger. Important to keep these larger lights cool and a safe distance from your plants to avoid burning the leaves.

Adjustable Ballasts

A good feature to look for in a ballast is the option to adjust the output wattage. For example the ballast I currently use has different settings: 250, 400W, 600w and “super lumens”

Grow light ballast with adjustable wattage settings.

When you are first starting off you can keep it on a lower setting. As the plants get bigger you can adjust the wattage accordingly.

Grow Room Glasses

When using HPS bulbs you will find it puts off a yellow/orange type of light. This is the perfect light spectrum to help your plants produce big, potent buds. One thing to remember is that when you check your plants the light will change the way they look. I would recommend buying a pair of growing glasses. The glasses come with special lenses which filter out the light and make it easier for you to see the true colour of your plants and also reducing strain on your eyes. These high wattage, HID ( high intensity discharge) lights can hurt your eyes after working near them, its best to protect them using a pair of glasses. You can see the difference in the picture below. The picture on the left is taken with no glasses. The picture on the right I put the glasses in front of the camera and you can see the difference it makes.

Comparing the light difference between two grow tents.

Other Tips & Tricks

Distance– Your lights should be approx 12-20 inches away from your plants. You can put your hand on top of your plant and if it feels too hot, move the light up a bit higher. You want to find a balance. Lowering the light makes it easier for the plant to receive the light, however too low and it will cause heat burn and the leaves will curl.

Cable Management – When installing your light fixture its important to keep your cables neat and tidy. These type of lights can heat up very quickly and if you have your cable touching the fixture it could cause it to melt.

Mount the Ballast – Once you have hung your light you will need to find a good spot to mount your ballast. I recommend attaching it to your wall or on a small piece of plywood. Remember the ballast contains electronics, make sure it is up off the floor to prevent water damage in case of a flood!


Choosing the right HPS bulb doesnt have to be hard. Make sure you find a suitable fixture and ballast, and simply buy the correct wattage bulb to match. Follow the tips and tricks in this guide and you will be ready to grow in no time!

If you have any questions or concerns please don’t hesitate to ask! Head over to the contact page. I respond to all comments and questions!

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