Grow Lights – Indoor Plants

This is a grow lights indoor plants guide and I will explain the different types of lights used for indoor growing.

It`s important to know that the temperature/color of the light is measured in Kelvin and the intensity of the light in Lumens.
The plants like best a Kelvin of about 2700k when growing (cool/blue) and 6500k (warm/red) while flowering.

If you are growing Cannabis, then you will need to switch the light to a 12/12h cycle for flowering, it is absolutely crucial that the plants get this 12h “sleep” every day, otherwise, the plant will be disturbed and might develop into a Hermaphrodite. (There will be more on this subject in a later post about the actual growing)

LED lights

LED lights have become more and more popular in the latest years as they have become better and better. There is Pro`s and Con`s with these lights as all others, they don’t produce much heat so you can cut down on your ventilation budget.

They also use less electricity than traditional HPS/MH, but I have yet to see a LED lamp do as well as HPS after using both types and many different Leds.
If someone promises you their Led light at 200w equals a 600w HPS, they are flat out lying to you. You need almost the same true wattage to get results like HPS.

Led lights can come with different spectrums, some let you switch between growing/flowering spectrum, and some are just full spectrum. Some also offer IR and UV light in their spectrum.

Led lights have a long lifespan (30 -50 000 hours)

Led light

HPS/MH lights

HPS/MH (High Pressure Sodium/Metal Halide) is the old workhorse and the choice for most indoor growers. You need a ballast to drive these lights and they do produce a lot of heat, so you need a good ventilation system when using HPS indoors. Ballasts and bulbs come in different wattage, some are adjustable too, the most common wattage is 250, 400, 600 & 1000w.
They can be used in combination with a closed reflector or a cooltube hooked up to the ventilation system blowing through the light and take the heat out.

A good rule of thumb when choosing a fan strong enough to manage the heat from HPS lamps is: Total Wattage / 2 +20%.
But that is minimum of what you should have, so if you use a 600 watt light 600 /2 + 20% = 320 M3h.
(M3h = Cubic Meter of Air the fan can move in 1 hour)

I recommend oversizing and connecting it to a fan controller (or get a fan with inbuilt controller) and rather run the fan at lower speeds because of noise.
A small fan at full speed makes a lot more noise than a big fan at half speed.

You can get bulbs dedicated to just the growing phase (MH) and just for flowering phase (HPS) or Full Spectrum that can be used for both growing and flowering. (HPS)
They offer great wattage per Lumens Ratio, but heating is a serious problem and the bulbs (tough cheap) don’t have such a long lifespan, they should be replaced about every 9 months or so if you grow continuously.

(The bulb will probably last for many years, but it loses power gradually, so you will gain more by replacing them regularly, I replace mine after every 3rd grow)

hps bulb

Fluorescent lights

Fluorescent lights are very cheap, but they are also very weak and therefore mostly used for cuttings/plants in the early stage.
They can be very successfully used in flowering too, but you will need 2 sets of bulbs/tubes as these don’t come in a mixed kelvin. They do however produce little heat.
They include a variety of different lamp types like T5/T8 tubes, PLL tubes, and CFL bulbs.
For the home grower, you will probably be using such a light for seedlings/cuttings, they are excellent for that purpose.

Some big grow company`s use only these lights to cover vast areas cheap, but as a home grower, it`s not very likely you will flower anything with these lights.
The tubes typically come in low wattage like 23 or 55w, while the CFL bulbs typically come in 125, 200, 250 & 300w.
They have a lifespan of about 10 000 hours.

T5 Tubes

Plasma lights

Plasma lights are one of the newest types of growing lights. They claim to emit a light that’s closer to the natural sun than any other type of lamps. They also like LED, use very little wattage compared to other lamps and produce almost no heat.

The con with this is that they are insanely expensive, I would not even consider such a light as a home grower.
I have not tried Plasma lamps myself, because they are so expensive, so I can’t tell you much from experience here.

Plasma lights work by using a light-emitting Plasma bulb that have a long lifespan (30 000 hours)


Lec Lights

These are pretty new on the market, they come in 2 variants, 315w or 630w.
They claim to be double as good as HPS and that a 315w can even outperform a 600w HPS with much less heat admitted also. (3-6 Celcius less than HPS at same wattage)Lec bulb
One good thing about these is that if you already got a HPS setup with ventilation and cooltube/closed reflector you only need a new Ballast and a new Lec Bulb, it will fit in existing gear with just an adapter.Lec Adapter
They are expensive tough, but the life expectancy of a bulb is about twice that of a HPS bulb, so you can reckon to grow at least for 18 months with these bulbs.
They also generate infrared and ultraviolet light which aren’t visible to the naked eye but have multiple benefits for cannabis plants, such as improving photosynthesis, increasing resin yield and generating more compact flowers.
Lec Light Spectrum:

Lec Spectrum

So what is the best light?

That’s very hard to say, I still favor HPS Full Spectrum bulbs for growing/flowering and 2x55w PLL tubes for seedlings/cuttings after more than 25 years of indoor growing.

Every type of light has its pro`s and con`s, it comes very much down to your budget and how much you are willing to spend on it. It also comes down to the size of your growing space and how many plants you plan to grow.

I hope this grow lights indoor plants guide has given you a basic understanding of grow lighting, you will learn more about it as you look at the different products and compare them.

Here at Hydroshopper we aim to deliver what we know to be best and give you the most bang for your bucks, you will not find cheap China LED lamps here that only will frustrate you.

Should you have any questions, leave a comment below and I will be happy to help you out!

All the best,


Founder of HydroShopper


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