Is a 150 w HPS too much for a Broom Closet?

by Sheila
(New York)

I am setting up a tiny garden in a 14 x 15 x 60 inch broom closet. It is 1.5 sq.ft and about 7.5 cubic ft. I'm hoping to grow a smallish tomato plant in there. Right now I have a few small plants and a jury-rigged setup of 3 compact fluorescent lights totaling 105 watts and 7050 lumens.

Today I closed the door and the temperature climbed to 115° near the base of the bulbs (the plants were probably a bit cooler). So, I obviously need a fan, and your fan/exhaust tutorial was very helpful!

I saw a 150 W HPS lamp (by SunSystems) on craigslist that I would like to get. The ballast is incorporated into the lamp housing (I know that's not good), but I'm trying to do this inexpensively. Your guide says that the max wattage for my room should be 120W. I'm planning to mount the exhaust fan at the ceiling of the cabinet and drill passive intake holes on the side. There won't be any duct work or tubes. Will a 150 W HPS light be too hot or too much light for my plant, or could I use a bigger fan to counter-act the heat? It would be nice not to have to deal with more jury rigged CFL's, plus I think I'll need more light when flowering.

By the way, I need to tell you how great your guide is. Great info, easy to navigate, easy to read, and it flows logically. There is so much misinformation out there I was grateful to find your site. Thank you so much, Sheila.

Answer: Sheila- light loving plants, like tomatoes, need a minimum of 40 watts/sq.ft. With additional light- up to 70 or 80 watts/sq.ft.- your plants will not need to grow as many fan leaves, and yet they are likely to produce a slightly bigger crop. This, of course, is assuming you can get your temperature under control.

Let's start at the low end. To get to 40 watts/sq.ft. your 1.5 sq.ft. closet will need a minimum of 60 watts. Obviously, the CFL's or the 150 w HPS light would be more than enough to accomplish this. Don't worry about using too much light....your plants will simply ignore the extra. Your main problem is going to be temperature. Unfortunately, this becomes a very tricky problem when you pack grow lights into small, enclosed spaces.

If the light was in the center of a big room, so much air would constantly be exchanging around the plants (and with the rest of the room) that heat might not be an issue. This works for two reasons....One- the convection heat is exchanged with a huge "buffer zone" (the large air volume in the rest of the room, which is much cooler)....and Two- there are no solid walls right up against your plants to absorb the radiant heat. Once the walls in your broom closet absorb enough radiant heat, the walls begin to put off their own convection heat... which makes it much more difficult to cool the space than simply using a bigger fan.

Having said that, a bigger fan is where you need to start. The quicker you can exchange the air in your closet with the larger volume of air in the other room, the less heat you will have left to deal with. Also, the cooler the air is in the larger room, the more effective this strategy will be. Faced with a similar situation once, I used to keep the AC in my apartment at 68 degrees! When that wasn't quite enough, I built a duct out of cardboard to direct some of the AC to the air intake of my grow box.

If you are not using any AC, this could be a real problem. There are two other things you can do that will make a difference. One- reduce the watts inside the closet to the minimum you need for healthy growth. Less watts will produce less heat. Two- isolate your light(s) from the rest of the closet space (either by using an enclosed reflector with exhaust vents and glass in the bottom, or else by installing a piece of glass in the closet between your lights and the plants) and than use two exhaust fans.... one to cool the lights and the other to exchange the air around your plants with the larger room.

If the air outside is 60 degrees or less, you could also use a small fan and some 4 inch ducting to direct the cooler air straight into your closet space. In this case, you will want to pay careful attention to the temperature outdoors and the resulting temperature in your closet. Not only is too much heat a bad thing, but too little heat is also! Either hook the fan up to a thermostat placed inside the grow room, or else buy a good indoor/outdoor digital thermometer and keep careful track of how the outdoor temperature affects your indoor temperature (I use a Sunleaves digital thermometer myself- very reliable and only 25 bucks). This strategy will only work as long as the temperature outdoors stays at 60 degrees or below...than you need to fire up the AC or else shut down the grow box.

So to recap, reduce wattage, increase air exchange, and introduce cool air. Try introducing the cooler air may find you do not need to reduce your wattage just yet! The ideal temp for the growing space is 68-72 degrees, although a few degrees either way will not hurt too much. Some plants even tolerate 80 degrees well. If you get to the point where you can exhaust the lights separately from exhausting the rest of the closet AND you are able to introduce cool air from outdoors, you should not have a problem (until it warms up outdoors).

I hope this helps- I know it is not exactly a simple problem to tackle! One final note...Google "HPS security light"- there are some store bought 150 w lights available for as little as $39.00. I believe these are also available at Home Depot or Lowes...possibly even Wal-mart, although I do not like funding the advancement of the police state through the purchase of their slave labor produced goods :( Happy Growing!

Comments for Is a 150 w HPS too much for a Broom Closet?

Average Rating starstarstarstarstar

Click here to add your own comments

Mar 24, 2010
HPS lights not very efficient after all?
by: Anonymous

Thanks, Jason! I just read on another discussion forum that the Sun System 150W HPS grow light uses 408 Watts after 60 minutes of use. (The inital start up was about 600W). This was posted by a distributor of Sun System who tested the light, so I tend to believe it, but I haven't been able to find specs from Sun System. The light is very bright (16,000 lumens), but if the fixture is so hot that I have to keep it far from the plants, it might not be worth it. (I learned that from one of your tips!) So, I'm going to stick with my CFLs for now. Maybe I'll start with lettuce or basil -- I want to grow something! I bought a small fan, but it is too powerful for the 2" passive intake hole that I drilled (the fan moves 80 CFM and I have 7.5 cu. ft!) So, I'm still tweaking. Thanks again for all your help! One way or another I will grow something I can eat!

Mar 16, 2010
Thank you, Jason!
by: Sheila

Wow, what great information! Maybe I need to start this project in November. I do have the window open a bit in that room, and as long as I keep the closet door open a few inches the temperature is about 78 F inside. But I won't be able to leave the door open when I start flowering, and that will probably be when it starts getting hot and sticky outside. I have an A/C in the room but I can't even get the temperature in my apartment down to 80 in the summer. Your idea of separating the lights and the plants with glass is great.

The HPS security lights are also a great suggestion. I noticed that they come in 70W & 100W fixtures, too. Would that be a wiser choice than 150W HPS or my 105W CFLs? This is a subject that confuses me. Should I judge lights by lumens or watts? I thought that HPS lights were more efficient than CFLs, generating more lumens per watt, so I thought I would have a cooler garden by switching to HPS lights. Or is it that CFLs somehow give off more heat per watt than HPS?

Response: Lumens are the measure of light that is actually usable to the technically, lumens are the measure by which to judge a light. However, when purchasing a grow light, it is safe to assume the majority of the light will be in the usable range for your plants (and so judging your light by watts is also very acceptable). I am not sure if one light puts out more heat per watt than the other. One thing that is certain, though, is that more watts produce more heat.

If I were you, I would give it a go with your 105 W CFL's. The 70 W HPS fixture would be a good choice also. I would be interested in knowing the lumen rating of each, as HPS lights are generally regarded as having a more intense, penetrating light than fluorescents. Either way, your heat problem will still be relatively the same, as the 35 W difference between the two is not that great. Good luck on your project, and Happy Growing!

Click here to add your own comments

Join in and write your own page! It's easy to do. How? Simply click here to return to Grow Lights Q&A.

All of the items that I personally use and recommend!

AffordableGarden Design&Setup

(10 week update below)

Find out the cheapest and easiest ways to garden productively in this article.

Hi everyone, Jason from Jason's Indoor Guide here. When I got started with hydroponic gardening more than 24 years ago, my first garden used rockwool cubes and B.C. Nutrients....and I remember thinking to myself yeah, sure, there may be a lot of advantages to gardening with hydroponics, for example there are very few pest problems, therefore very little pest control, no weeding, no plowing or tilling the soil, no soil testing or having to add things into the garden soil, no watering the garden....but for someone who just wants to grow their own vegetables and have more control over their food supply and the quality of the food that they eat, the cost of constantly having to buy grow media and hydroponic nutrients makes this an expensive hobby for most people...

Epic Nutrient Change

I suppose when you take into consideration how much money you save NOT having to buy food at the grocery store, it is surely cheaper to grow your own food hydroponically even with the cost of high quality nutrients. Nevertheless, I didn't have a whole lot of money to work with and I needed to make my efforts as affordable and effective as possible....and in the last 24 years I HAVE learned a thing or two!

As you browse through Jason's Indoor Guide, you will notice all of the systems that I use personally are homemade systems. As I got 3 or 4 years of experience under my belt, I quickly adopted a preference to standing water systems and systems that use expanded clay pellets or lava rock, because the media is re-usable and it eliminates a huge operating expense. So once a hydroponic system is built, garden maintenance is minimal- check and adjust the nutrient solution daily, and to change it completely every 2 weeks....and the biggest operating cost is the hydroponic nutrients. (and the electric bill, lol)...

Homemade Cloner

And, regarding the cost of the nutrients....I experimented for about 3 years with making different compost teas and nutrient teas, but there is still a lot of expense $$$ associated with making high quality nutrient kelp meal, liquid seaweed, rock dust, bat guano, un-Sulfured molasses, worm castings. You can eliminate a lot of this expense by becoming an expert at making high-quality colloidal humus compost, and use your properly made compost as the basis of your hydroponic nutrient solution.

Unfortunately, I have been gardening for over 24 years and I have only just recently mastered this difficult skill....and even then, only because I happened to find a very easy to follow, high quality technique and decided to follow the instructions to the letter. I produced more high quality compost in just one week than I was able to use in a whole year! If you can master the technique, I highly recommend it. It is one of the top 3 things you can do to increase the productivity of your food production efforts, while at the same time decreasing the amount of effort required to grow all of your own food, and decreasing the total cost of operating your food production system.

And when I say decrease operating costs, I mean decrease them to almost ZERO, especially if you are producing your own nutrients...

High Efficiency

The ultimate solution to eliminate the cost of your hydroponic nutrients: Imagine a hydroponic system that does not require you to buy any nutrients, does not require you to make your own compost, and does not require you to brew your own nutrient tea. Seriously! No cost and no effort as far as providing nutrients to your plants! Plus, at the end of the gardening cycle you harvest all of your garden vegetables, PLUS YOU HARVEST FISH from the system--->


Click Here to learn more!

This solution is aquaponics. If you are serious about producing all of your own food and being self-sufficient, this is the ultimate solution for reducing expenses (as much as possible), reducing the total amount of work required, and maximizing the productivity of your gardening efforts. I have been gardening for over 24 years, and it is the perfect food production solution in my opinion.

Produce garnden vegetables AND fish together. Eliminate fertilizer costs!

Besides mastering how to make high quality compost, learning aquaponics is one of the top 3 things you can do to increase your garden productivity, reduce your total costs, and reduce your total work. The product that I learned from is called Aquaponics4you. With all of my hydroponic gardening experience, the first time I came across the Aquaponics4you product I knew immediately that it was something very special! Place an aquaponics system outdoors and use the sun instead of grow lights, and you have reduced every garden expense to nearly ZERO!

The Same System/ 10 Weeks Later!

If you've found this site helpful at all, I would really appreciate it