3000K vs 3100K vs 4000K vs 4200K

3000K vs 3100K vs 4000K vs 4200K: Which Light Is Suitable?

Grow lights are very popular for indoor hemp plants. But with the diverse options, it is hard to choose the perfect one.

So, which is better 3000K vs 3100K vs 4000K vs 4200K?

Among the four grow lights, 3000K is the warmest grow light, then comes 3100k, 4000k, and 4200k respectively. The 3000K and 3100K lights are yellow whereas 4000K and 4200K lights are white. Plants under 3000k and 3100k tend to grow taller than 4000k and 4100K. But, 4200K has the highest PPF per watt count among the grow lights.

Even though this information is very useful, it isn’t enough. That’s why I will cover everything in detail for you.

So, let’s get started.

Quick Comparison

With the versatile option of grow lights, choosing the best one can be tough. Because each hemp plant requires a different source of light. But, the Ceramic Metal Helaide (CMH) lamps are very reliable.

There are significant differences between 400W, 600W, and 1000W HPS grow light. Similarly, 3000K, 3100K, 4000K, and 4200K grow lights have differences too. But, what are the differences between 3000K, 3100K, 4000K, and 4200K grow lights?

Let’s see a quick comparison between these grow lights. 

Differentiating Factors3000K3100K4000K4200K
TemperatureColdestCooler Than 4000KCooler Than 4200KWarmest
ColorBright YellowSoft Yellow GlowSoft White GlowBright White
Plant LengthTallestLess Shorter than 3000K Plants under 3000kLess Shorter than 3100K Plants under 3100kLess Shorter than 4000K Plants under 4000k
Vegetation RateFastestSlower than 3000kSlower than 3100kSlower than 4000k
NodesLess Tight than 3100KLess Tight than 4000KLess Tight than 4200KTightest
PPF Per Watt1.50 PPF1. 95 PPF2.20 PPF2.75 PPF
Initial Lumens32,900 Lumens33,000 Lumes33,500 Lumens34,300 Lumens
CRI Rating90929597
Lumen Maintenance RateLowestHigher than 3000KHigher than 3100KHighest
PriceCheck Now on AmazonCheck Now on AmazonCheck Now on AmazonCheck Now on Amazon

The quick comparison gives many hints. However, it isn’t enough to jump on to a conclusion. 

Source: leafly.ca

You need to dive in-depth to gain proper knowledge. Hence, in the next section, I will compare those head-to-head.

So, let’s move on.

Head-to-Head Comparisons

In this section, I will compare the 3000K, 3100K, 4000K, and 4200K grow lights. Because under each light, the hemp plant grows differently. So, it should be your best option to choose according to your own method of cultivation.

Before I start the comparison there’s an important factor you should know. Knowing about autoflower’s veg or bloom light suitability is necessary.

With that said, now let’s talk about the head-to-head comparison.


One of the significant factors is the temperature of grow lights. Grow lights get hot over time. This can have a negative effect on the hemp plants. So, let’s talk about the temperature first.

3000K grow light tends to get hot easily. If your light source is close to the hemp plant, it can burn. However, sometimes for fast growth, it is advised to use strong lights as you can see here-

On the other hand, 3100K is slightly cooler than 3000K. But the margin is very little. Again, having the 3100K light close to your plants can be harmful. 

However, 4000K grow lights are on the cooler side. The lights can be cooler than 3000K and 3100K grow light.

Nevertheless, 4100K grow lights are the coldest. So, your hemp plants are more secure under the 4100K light bulb.

Summary: The 4100K is the coldest in terms of temperature.


Grow lights with different colors affect the hemp differently. Hence, I will talk about the color each grow light produce.

The color of 3000K grow light is bright yellow. It has a full spectrum from 350nm-800nm waves. It can also give 600nm red light.

On the other hand, the color of 3100K grow light is soft yellow. This light can boost the subtle growth of vegetation.

Moving on, the color of 4000K grow light is soft white. It gives your indoor farming an aesthetic look nevertheless.

Source: herbiesheadshop.com

Lastly, the color of 4200K grow light is bright white. The 4200K grow light bulb is very beneficial for the budding phase.

Summary: The colors 3000K and 3100K are yellow. Whereas the color 4000K and 4100K are white. 

Plant Growth Type

Indoor hemp plants’ growth largely depends on the light source. Different power, color, and even electrical outlet of lights directly influence the growth. So, let’s talk about the plant growth type under each light.

Using a 3000K light, you will see that the hemp plants tend to get taller. It is because the light source forces the plants to seek more energy. As a result, they get closer to the light by getting tall.

Albeit, a hemp plant under 3100K will grow slightly shorter than a plant under 3000K light. The reason behind this is that 3100K light has a better light spectrum.

One thing you should keep in mind is that the quality of 3100K light varies from brand to brand. We’ve researched about it a lot and found some brands whose light quality is consistent. 

Here are some of our top picks for 3100K lights: 

Nevertheless, a 4000K grow light has an even better light spectrum than 3100K. This enables the plant to grow wider and gives vibrant color.

Yet, under a 4200K grow light, your hemp plant will look stunning. It will be very healthy, mature, and vibrant.

Summary: The 3000K and 3100K enables height growth. But, 4000K and 4100K enables more vibrant and wide growth.

Vegetation Rate

Hemp is an annual herb. So, the vegetation period of hemp lasts between 3 to 4 months. 

However, the vegetation rate of cannabis can be affected by grow lights. So, let’s see how each light influences the vegetation.

The 3000K light is a great catalyst for better vegetation. The warm yellow light and red color wave can significantly boost the vegetation rate. Nevertheless, you will have a proper and healthy plant after the end of the vegetation period.

On the other hand, 3100K light is on par with 3000K light. But the vegetation period can be boosted very well by bright and warm yellow light. So, the vegetation rate can be slow with it. Regardless of all, you will have healthy plants.

Now from the speculation, both 4000K and 4100K light sources act normally during vegetation. Because the lights will bolster the hemp to grow healthy. But, it doesn’t have much effect on vegetation rate.

Summary: The 3000K and 3100K lights significantly boost the vegetation rate. But, the 4000K and 4100K fail to do so.

Actual Lumens

The lumens of light are very important. That way you can know how much light your plants will get. So, let’s talk about the actual lumens.

The actual lumens of 3000K light is 32,900 lumens. This is very bright and adequate enough for your hemp plant.

Moving on, the actual lumens of 3100K light is 33,000 lumens. This is slightly brighter than 3000K light.

However, the 4000K lights can illuminate at 33,500 lumens. This can have a more significant impact on your plant than 3000K and 3100k light.

Albeit, the actual lumens of 4200K lights are 34,300 lumens. This is one of the brightest light sources for your hemp plant.

Summary: The 4000K and 4200K are brighter than 3000K and 3100K.

CRI Rating

Another important thing to consider is CRI rating. CRI or Color Rendering Index can give you the idea of what light you actually need. Hence, I will address the issue right away.

The CRI rating of 3000K light is 90. This is close to sun’s CRI rating which is 100. So, 3000K light is more than capable of having an effect on plant growth.

However, the CRI rating of 3100K light is 92. This is better than the 3000K light’s CRI rating. 

Yet, 4000K lights have better CRI than 3000K and 3100K lights. The CRI rating of 4000K light is 95. As you can tell, it is a very good rating for a grow light.

Source: bigbudsmag.com

But to everyone’s surprise, 4200K lights have a CRI rating of 98. This is very close to the sun’s CRI. As a result, 4200K lights influence photosynthesis more than other lights.

Summary: The 4200K light has the best CRI rating. Then comes 4000K, 3100K and 3000K respectively.


In the last section, I will talk about the cost of setting up each light system. Because the budget is an important factor to consider. Otherwise, you won’t be getting the best out of what you purchase.

The price of a 3000K light ranges between $60-$110. Some of the best 3000K grow light bulbs that we’ve seen are given below.

Now, the 3100K light will cost slightly more than 3000K light. The price ranges from $75 to $120. Lastly, the price range of 4000K light is $60-$120. And the 4100K light ranges between $70-$130.

Summary: 3100K grow light costs slightly more than the rest.

That’s all regarding the head-to-head comparison. Also, knowing the differences between HPS and CMH grow light is important for a better decision.

Let’s move on to the final section.

So, Which Light Is Better?

So, which light should you go for your hemp plants? Well here’s a short table for you that will give a short overview of the whole debate:

If you are looking for better vegetation and budding, 3000K, or 3100K lights are best. However, for vibrant and mature plants, go for 4000K, or 4200K lights. Also, the 4000K and 4200K lights keep the temperature low.

Nevertheless, the CRI of 90+ is provided by every light. So, your plants’ growth will remain constant throughout.

Whatever you go for, it will significantly have an impact on your plants.


How Long Does Hemp Take to Start Growing?

If the relevant measures are taken, hemp plants will start budding in 1-3 weeks. Afterward, the plant will be available in 1-8 weeks after blossoming. But, each plant has its growth phase. Some take more than 3 weeks to begin budding. Yet, by taking the right steps, you can grow healthy hemp plants.

In What Sort of Environment Does Hemp Flourish?

Hemp thrives in a warm, humid environment. Seed germination and the young plants require enough soil moisture. Having enough light for indoor plants is critical. Hemp plants can decay without proper care. So, provide hemp plants with water, air, and light. Also, always remember to fertilize the land.

Can Light Cause Any Damage to Hemp Plants?

Yes, excessive light can harm your hemp plants. Grow lights tend to get hot over time. This causes the air to get warm too. That’s why you should keep lights on for 8-12 hours. However, if the light remains on all day, the plants can die. Because the plants will produce more energy than necessary.


That’s all regarding 3000K vs 3100K vs 4000K vs 4200K. Hopefully, now you will be able to choose the perfect light setups for your indoor farm.

Here’s a piece of a tip, if possible let the outside air come inside. That way, your plants will have the perfect weather required.

Have a good day.

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