#### UncleCannabis

##### New Member

**How to Select the Right Mars-Hydro LED Grow Light for Your Specific Gardening Needs**

**Case Study - Grow Space Size: 4' wide x 4' Long x 6'6" High**

How do I determine the square footage of my grow area?How do I determine the square footage of my grow area?

Measure the floor space that you'll be looking to illuminate with your future LED light and hopefully fill with sticky buds someday.

Multiply the length times the width and this will give you the square footage. Since the grow space indicated in our case study is 4' long by 4' wide we would multiply 4 times 4 which equals to 16 square foot of grow space.

Length (4') x Width (4') = Total Square Feet (16')

*How many actual watts of power will it take to for me to grow decent or high quality meds?*You should be able to get good results with as little as 20-25 actual watts of power per square foot of grow space with the light set about 18" above the canopy during bloom.

If you want to step up your game, increase yields, and grow really thick and dense nuggets with higher resin content then you'll probably want to be somewhere around 30 to 50 watts of actual power per square foot during bloom with the lights set approximately 18" above the canopy.

In general, the more power per square foot, the better the quality of the finished product.....within reason of course.

Yes, there is a such thing as too much light. Anything over 50 actual watts per square foot would likely require CO2 supplementation and heat issues would need to be adequately addressed.

*For the same light, Mars-Hydro gives two different numbers for actual watts. How do I determine how many actual watts to use for my calculations?*Visit the Mars-Hydro website and select the light you are interested in evaluating. For the purpose of this exercise we'll evaluate the Mars2 700 Watt light.

Now check the following:

How many actual watts does the light draw? The website list 300-380 watts power draw. This means that the light will draw approximately 300 watts if using a 220volt/50Hz electrical grid or 380 watts if using 110volt/60Hz electrical grid. For the purpose of this exercise we will use 380 watts as our wattage draw number.

*What is the effective illumination area at 18"?*Note that the effective illumination area for the Mars2 700 is shown as 3.5'x3.5' @ 24".

But remember, you'll usually want to have your lights set at 18" or less during bloom not 24". So 3.5'x3.5' (12.25 sq/ft) is not the number that you'll want to be using to evaluate this light if you want to use it for flowing.

Scroll down a bit on the web page and on the lower right side of the web page you'll see this illustration.

This illustration shows how the light intensity increases and the effective illumination area decreases as the light gets nearer to the plant canopy. This is why you'll want to set your light as low as possible during flower without burning your plants.

Per the illustration you'll find that the Mars2 700 watt light delivers about 9880 LUX at 50cm or 19.6". This is the approximate distance that you'd want this light set during bloom.

So effective illumination for this light when used for bloom will be less than 3.5'x3.5' as stated in the specs.

The actual effective illumination area when using this light for flowing would be about 3'x3' or 9 square foot.

*So....now that we know how much space we need to illuminate (16 sq/ft), we know the actual wattage the light puts out (380 watts), and we've determined the approximate effective illumination area for this light when used for flowering (9 sq/ft)....what now?*Take the actual wall watts that the light draws (380 watts) and divide this number by the effective illumination area with the light place 18" above the canopy (9 sq/ft).

380 watts divided by 9 sq/ft = 42 watts per sq/ft

So this means that the Mars2 700 watt light would deliver approximately 42 watts of actual power per square foot when set approximately 18" above the plant canopy.

42 watts per square foot will grow some really fine medicine. But if you recall, our grow space is 16 sq/ft. In order for this light to illuminate 16 square feet we would need to raise it to about 32" or more above the plant canopy. Now moving the light further from the canopy will light up more area but it will also result in less light intensity at the plant canopy or less wattage per square foot.

380 watts divided by 16 square foot = 23.75 watts per square foot. Can you still grow pot with 23.75 watts per sq/ft. Sure you can, but yields and bud density will not be as good as they would be with a larger/more powerful light.

*So now let's go ahead and take a look at the Mars2 1600 Watt light.*This light has an actual power draw of 780 watts when plugged into a 110 volt grid.

Lets assume that the effective illumination area at 18" above the canopy would be approximately 4.5'x4.5' or 6" less in all directions than what is stated on the website for a light being set at 24".

4.5'x4.5'=20.25 sq/ft

So we would take the actual wattage (780) and divide this by the effective illumination area at 18" above the canopy (20.25 sq/ft) to determine the watts per square foot.

780 watts divided by 20.25 = 38.5 watts per square foot.

At 38.5 watts per square foot this would allow you to grow top quality buds with large yields.

But wait, our grow space is only 16 sq/ft remember. So if we set this light at 18" above the canopy we still come up with the same answer of 38.5 watts per sq/ft but we now have light spilling over onto the walls since the effective illumination area is larger than our space. This will result in some of the light being reflected back onto the plants so the actual light being delivered to the plants will actually be a tad greater than 38.5 watts per sq/ft. Don't ask me how to calculate reflected light unless you want a B.S. answer.

On the other hand, if your plants can handle the light being lowered to 12" above the canopy which they often will you'll end up with a perfect fit in regards to effective illumination area of the light versus grow space size. With the light lowered to 12" above the plant canopy the effective illumination would now be reduced from 20sq/ft to 16sq/ft, the exact size of our grow space. In addition, your watts per square foot will increase to 48.75 watts per square foot since the the light is now closer to the plant canopy.

780 watts divided by 16 square foot illumination area (reduced illumination area caused by dropping the light to 12" above the canopy) = 48.75 watts.

This light would be about as large and powerful as you'd want to go for this size grow space. Anything more powerful than the Mars2 1600 for a 16 sq/ft grow space would likely be overkill and only result in wasted electricity and heat issues.

__**Note - LED's may run cooler than some other lighting options but they do generate heat. Be certain that you are able to address heat issues.__Assuming that your gardening skills are up to par, you'll be able to grow top quality buds with this lamp so this lamp may be a perfect fit for your needs.

However, if you are on a tight budget, trying to minimize heat inside of your grow space, or minimize electrical usage you could certainly go with a less powerful light and still grow high quality produce.

*Now lets take a look at the Mars2 1200 watt light.*520 actual watts using 120 volt power supply.

Effective illumination area for flowing with this light would be approximately 4'x4' or 16 sq/ft.

520 watts divided by 16 sq/ft = 32.5 watts per square foot.

This light would be a nice fit for anyone looking to grow good quality medicine with the expectation of respectable yields in a 16 square foot grow space. This light is not too powerful but not too weak either and it will not generate as much heat in your grow space as the Mars2 1600.

This light would probably be the "sweet spot" for most hobby growers.

*Should I go with 5 watt or 3 watt diodes?*The 5 watt diodes should allow for deeper penetration into the plant canopy resulting in less "larf" or airy buds below the main canopy. As a trade off, the 5 watt diodes may result in more heat compared to 3 watt diodes.

Note that I've seen some really fine crops grown with the 3 watt Reflector Series lights.

3 watt or 5 watt would be based on the personal preference of the end user. Also note that LED lighting technology is constantly evolving so what holds true today may be completely different next week.

*For larger areas should I go with a single large panel or multiple medium to small lights?*In general it would be best to use multiple lights instead of a single light panel. The reason for this is improved lighting coverage. With all or most LED lights the light intensity at the canopy is greatest near the center area of the effective illumination area. In other words if the effective illumination area of the light is 9 square feet, the middle area of this 9 square feet (about 4 sq/ft or so) will be much more brightly lit up with light intensity diminishing rapidly as you move further away from center. This results in buds located nearer to the center of the light having better growth / thicker denser buds with bud quality diminishing as you move further away from the center of the effective illumination area.

Using multiple lights allows you to better distribute the intense light in more areas of the grow space instead of having all of the higher intensity light concentrated in only one area while the outer edges never receive intense light.

It also allows you to minimize low light areas by having the ability to move individual lights around as needed in order to minimize light gaps or dark/shaded areas.

I hope this makes sense to everyone.

Anyways, I do hope this helps those that may be new to LED lighting technology to properly evaluate all of the different Mars-Hydro LED light offerings and determine which light would best suit your needs and available grow space.

Hopefully this will also result in less Q&A sessions for Sara.

Sara,

Please feel free to chime in and correct me if I've stated anything that may be incorrect or misleading.

Happy gardening friends!