The Best Time to Change Your Grow Light Bulbs

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Editor’s note: This article was originally published in June 2020. It has been updated for accuracy and comprehensiveness as of August 2023.

It’s important for your grow lights to operate at their full potential at all times. Your grow light’s intensity is a pivotal component of a healthy indoor garden.

Make sure you check your bulbs and ensure they're running at maximum efficiency for maximum growth.

Unfortunately, though, depreciation in lumen output and a shift in color spectrum is inevitable over time. As a result of this, you’ll need to replace your grow light bulbs eventually.

But how do you know when your plant light bulb has run its course? And why will its power degrade in the first place?

Below, we’ll cover everything you need to know about when and why you should swap out your grow bulbs. We’ll even suggest some of the best grow bulbs around for when the time comes.

Table of Contents

  1. The Best Replacement Grow Bulb Options
    1. Yield Lab Grow Bulbs Are the Most Dependable Around
    2. Digilux HPS Grow Bulbs for Intense Red Spectrum
    3. USHIO Bulbs for Supercharged HID Grow Lights
    4. Why Should You Use a Grow Bulb with a Dimming Ballast?
  2. How Do Grow Lights Work and Why Do They Depreciate?
    1. How Long Do Grow Light Bulbs Last?
  3. How Do You Know When It’s Time to Change Your Grow Lights?
    1. Loss of Lumens = Loss of PAR
    2. Flickering Grow Light Bulbs Lead to Burned Out Bulbs and Stunted Growth
  4. Grow Bulb 101: Other Factors to Consider

The Best Replacement Grow Bulb Options

When your grow light bulbs eventually start to flicker, fade, and die, don’t fret! You have several options to tackle the issue with.

Here are a few replacement grow bulbs to consider based on the type of grow light you have:

1. Yield Lab Grow Bulbs Are the Most Dependable Around

You’re going to want a dependable grow bulb whether you’re growing with an HPS, MH, CMH, double-ended, or T5 grow light. Yield Lab grow bulbs offer a wide range of styles, wattage, and PAR, so you’re sure to find a good fit for your grow light when it’s time for a replacement.

Yield Lab HPS 1000w Lamp HID Bulb for grow rooms and grow tents.

Yield Lab 315w 3100K Ceramic Metal Halide (CMH) Grow Light Bulb for indoor grow rooms and grow tents.

See Our Full Selection of Yield Lab Grow Bulbs for HPS, MH, CMH, and T5 Grow Lights Here

2. Digilux HPS Grow Bulbs for Intense Red Spectrum

Are the bulbs in your HPS grow light losing their luster? If you’re looking to make sure your plants are getting all the lumens and the red spectrum they need with some fresh new lights, Digilux grow bulbs are the way to go.

Digilux Digital High Pressure Sodium (HPS) Lamp, 1000W, 2000K for grow tents and grow rooms.

  • These single-ended HPS bulbs give off a deep, intense red spectrum with a color temperature of 2000k that’s sure to help your plants thrive and produce plentiful yields.
  • Digilux also offers a double-ended HPS bulb, also with a 2000k color temperature.

See Our Full Selection of Digilux Grow Bulbs for HPS Grow Lights Here

3. USHIO Bulbs for Supercharged HID Grow Lights

If you’re looking to get the maximum power possible from a bulb for your supercharged HID grow light, you’ll want a USHIO bulb.

USHIO Hilux Gro 315w CMH Lamp - 3000k for indoor grow rooms and grow tents.

See Our Full Selection of USHIO Grow Bulbs for HPS and CMH Grow Lights Here

How Do Grow Lights Work and Why Do They Depreciate?

When your bulb's base shows sign of wear, check your bulb's illumination because they may be wearing out.

To understand how grow lights fade, as well as when they’ll eventually need to be replaced, you’ll first need to understand what the grow bulbs are made of and how they work. High pressure sodium (HPS), metal halide (MH), and ceramic metal halide (CMH) lights are all powered by gas, and their light spectrum is determined by the specific chemical composition that each bulb contains.

  • These gas-powered bulbs — also known as HIDs, or high-intensity discharge lights — work when a ballast is heated to send an electric arc between two electrodes that are held in what’s known as an arc tube.
  • This arc tube is filled with different gases and metal salts, which, as previously mentioned, determine the bulb’s wavelengths and color spectrum.
    • HPS grow lights, for example, feature an aluminum oxide ceramic arc tube. This arc tube contains chemicals like sodium, mercury, and xenon that create a lot of yellow, red, and far-red in their light spectrum. This makes HPS lights ideal for flowering plants.
    • Meanwhile, MH bulbs contain high amounts of metal halide in their quartz arc tube, which gives off a cool, white light when heated. This produces a spectrum with a good amount of blue wavelengths, making MH bulbs a good option for when your plants are in the vegetative phase.
    • The chemicals in CMH grow lights — which operate like MH lights but have a ceramic arc tube like HPS grow lights do — offer a relatively full color spectrum with high amounts of red, yellow, and green. However, CMHs don’t offer high amounts of the blue light that’s ideal for the vegging stage.

How Long Do Grow Light Bulbs Last?

While each of these grow lights offers a unique chemical composition and color spectrum, they also have different life expectancies based on these factors.

  • HPS Grow Light Lifespan: An HPS grow bulb will generally degrade at a significantly slower rate than its MH counterpart. You’ll get a good 24,000 hours out of an HPS lamp. When they do start to degrade, though, HPS bulbs tend to depreciate in their blue spectrum output first. They typically need to be replaced about every 10 to 14 months.
  • MH Grow Light Lifespan: After 20,000 hours of use, an MH grow bulb will have depreciated twice as much as an HPS grow light bulb. For this reason, MH bulbs will likely need to be replaced every 6 to 10 months or so. 

Your grow bulb’s intensity is bound to deplete over time. No matter how well you take care of your grow lights or what sort of conditions you maintain in your grow room or grow tent to keep things running at optimal levels, this is inevitable.

Grow light kit with double-ended HPS grow light bulb.

This is due to the physical changes in the lamp — also known as electrode deterioration — and changes to the chemical balance of the metals contained in the bulb’s arc tube. Over time, usage alone will wear them down and deplete the life of your HPS, MH, or CMH bulb.

A big contributing factor to the deterioration of your grow light bulb is the way it’s fired up: Each time an HID lamp is started, the ballast sends a huge voltage blast through the grow bulb, causing slight damage to the lamp every time.

As time goes by, this leads to significant electrode deterioration. The chemical balance and properties of the arc tube change, and, in turn, the intensity of your light decreases and the color spectrum shifts. This will typically happen over the course of 6 to 12 months, and it happens from use alone.

That’s why it’s important to know the signs of a fading plant light bulb and what to do when you run into a dying grow lamp.

How Do You Know When It’s Time to Change Your Grow Lights?

So how do you know when your grow light is reaching the end of its life? There are two telltale signs to look out for to know when your grow bulb is in need of some attention.

Loss of Lumens = Loss of PAR

Bright HPS grow bulb.

The first sign of a dying grow light bulb is a reduction in lumen output (or brightness). Lumens are the unit used to measure light emitted from a source (like a grow bulb).

Though this might sound scientific and complicated, it’s actually not too difficult to notice if you’re paying attention. Your grow light will look dimmer over time — the more you use it, the more it fades.

A loss of lumens and overall light intensity can be detrimental to the health of your plants.

When you first buy a grow light, it’s at its optimal intensity and lumen output. As such, you can be sure it’s doing its job and providing your plants with all the light they need — given you chose a suitable light for your plants, that is.

Dim HPS grow bulb.As your grow light’s initial lumen output decreases, its ability to properly sustain your plants diminishes. This can affect your grow room more than you may think: The loss of light will have a directly proportional effect on your yields, meaning if your lamp’s light output reduces by 5 percent, you’ll also see a 5 percent drop in your yield.

Keep in mind that some light reduction is normal and inevitable throughout the life of your garden and your HID light. That said, it’s best to consider swapping out your grow bulb when its lumens start to drop dramatically.

You can measure your grow bulb’s light output using a quantum meter or integrating sphere. These devices are designed to let you know how many photons your grow light is emitting.

Flickering Grow Light Bulbs Lead to Burned Out Bulbs and Stunted Growth

Burnt out HPS grow bulb.

In addition to a decrease in the overall brightness of your light, the second sign of deterioration you’ll want to look out for is a flickering light bulb that will eventually turn off altogether.

Don’t worry: It’s not a problem with your electricity or a ghost in your indoor grow room! A flickering light just means your grow bulb is dying, and it’s time to switch it out.

  • A flickering grow light isn’t just annoying — it can also lead to lighting issues that can disrupt your grow room’s light cycle.
  • This disruption can significantly hinder the growth of your plants, and it can even stunt flowers and fruit.

Your plants typically need to maintain a regular light cycle in order to thrive like they would if they were growing in natural sunlight. The sun doesn’t flicker, so a flickering grow light is an issue you shouldn’t ignore.

Why Should You Use a Grow Bulb with a Dimming Ballast?

 

First thing’s first: Before we get to replacement grow bulbs, we need to discuss your HID grow light’s ballast.

Your ballast is something you’ll want to keep in mind when you notice flickering grow bulbs.

Grow light ballast with Super Lumens feature.

Some dimmable ballasts, like Yield Lab’s 1000w, 600w, and 400w Digital Dimming Ballasts, include a Super Lumen feature. If you’re using a grow light with one of these ballasts, it’s a good idea to make use of this feature.

This will give your grow bulb an extra boost by spotting it a little more energy than it receives at 100 percent. This comes in handy when your grow light bulb starts to die, because it can make up for some of the lumens it’s lost.

If your grow light kit doesn’t include a dimming ballast, it’s definitely worth investing in one. Being able to fall back on the Super Lumen feature when the time comes around will ensure solid light intensity even if your grow bulb starts fading.

Keep in mind, though, that the more you use this feature to push your grow light, the more the bulb’s life will be reduced.

Grow Bulbs 101: Other Factors to Consider

While your grow light bulbs are bound to eventually deteriorate in power just from use alone, there are other factors that can cause them to fade at a faster rate.

HID grow light - HPS grow light bulb.

  • Colder temperatures, for example, can have an adverse effect on the quality of a grow bulb. Grow lights are designed to operate at higher temperatures, so even strong breezes can lead to dimmer output than usual when it comes to double-ended grow lights.
  • The age and type of ballast you use to power your grow lights can also contribute significantly to a grow bulb’s depreciation.

So if you want to ensure your grow lights have the longest, most powerful life possible, it’s important to keep an eye on all of the factors that can cause deterioration. Make sure you keep the conditions of your grow room as ideal as possible. You’ll also want to ensure optimal usage levels in order to maximize the life and the lumens and wavelengths of your grow bulb.

When it’s finally time to make the switch, give one of our grow light suggestions a shot! They’re all great grow bulbs that are sure to last you a very long time.

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