# Heat output of 300w CFL vs 400w or 600w HPS?



## emrldthumb (Feb 1, 2015)

I've put as much as 310w of CFLs (mostly 42w each) in my grow room without running into any heat problem. However, my exhaust fan is just a duct booster rated 80 cfm, and I'm worried it won't be up to the task if I upgrade to a 400w or 600w HPS. 

Is there an easy way to calculate how much heat a particular wattage of CFLs or HPS lamps produce on average? I know I need to get a good centrifugal/can fan at some point, but I'm trying to figure out if it can wait a little longer. I'm guessing it's mandatory even for a 400w, but I prefer to do the math rather than rely on gut reaction. 

FYI, the grow room is 30" wide by 7 ft tall by 10 feet long, but I'll only be using the last 3 feet or so instead of all 10 feet.  The attached photo shows the space, there will be a second container so that the whole black drip tray will be the grow space. It measures 28" by 48". 

View attachment IMG_20150130_224716_noexif.jpg


----------



## The Hemp Goddess (Feb 2, 2015)

I really cannot tell you the heat difference, but it will be a more as you are getting way way more light.  But these are really not fair comparisons to begin with--kind of like comparing the sun in the northern US on Dec 21 compared to the sun at the equator June 21 and wondering if the equator will be hotter.  Yes, of course.  310W of CFLs are only putting out about 20,000 lumens, maybe less.  Compare that to a 400W HPS that will be emitting 50,000 or so lumens--250% more light for less than 25% more power.

Because of reasons like this, I do not use CFLs and never will.  However, as you can see, you are paying over twice as much per lumen in electricity running CFLs over HPS.  In addition, the CFLs will give you substantially less bud than an HPS is capable of.  You will need to upgrade your duct booster fans to real exhaust fans, but the difference in yield should be dramatic.


----------



## emrldthumb (Feb 2, 2015)

Yeah I mean that's why I called it an "upgrade"... I'm just trying to decide whether I can get the light without a new fan or whether I'll need to buy both at once.  I guess I can start with the light and if it gets too hot, just switch back to the CFLs until I can get a better fan. 

I've been happy enough with CFLs for years now, always harvested more than I could smoke myself, but this time I'll be giving some to a friend with MS so I need to increase production a little over what I'm used to, and I've become fond of making a tincture, which also seems to blow through the supply a bit faster than smoking.


----------



## The Hemp Goddess (Feb 3, 2015)

You will need a fan from the get-g0.  A 400W is going to give you 250% more light.  It will cause more heat.


----------



## emrldthumb (Feb 3, 2015)

Yes, more heat, but right now my maximum temperature is around 75F in the grow room vs 65F ambient, so I could take some more heat before I start pushing the limits. Plants might even like it.  Come summer, I will certainly need a new fan, but I should be able to get one by sometime this spring if I get the light now. I was just trying to quantify how much more heat a 400w would put out since I've never used them. I.e., if the CFLs are raising the temperature 10F, would the HPS raise it 20F over ambient? That kind of thing. 

I guess I'll just hold off and get both together rather than try to do it haphazardly though.


----------



## The Hemp Goddess (Feb 4, 2015)

IF (and that is a big if) you had as many lumens in CFLs as the 400W HPS you would be getting substantially more heat.  However, very few CFLs growers actually get their lumens up where they need to be because it simply takes so many bulbs....and creates so much heat....and it so expensive. 

I really don't know how to answer because you are comparing cherries to watermelons.  You are talking about being inadequately lit compared to be adequately lit.  The only thing I can tell you is that if you are serious about this hobby then you want to step up to better lighting.  Rather than underlight because of heat, you need to deal with the heat so that you can get adequate lighting in there.  You will need as decent centrifuge type fan to deal with heat.  

Here is the bottom line.  You have 9.3 sq ft (28" x 48").  This is going to require 28,000 lumens for veg and 46500 for flowering.  To get this from CFLs, you are going to require approx. 10 42W or veg (420W) For flowering, the number of bulbs goes to  bulbs 17+ bulbs (714W). If you do want to step your grow up to where you have minimal lighting, it is going to take so many bulbs that the temps would be horrendous--700W creates a whole lot of heat, not to mention the waste in electricity.  A 400W MH will give you at least 36.000 lumens, a 400W HPS 50,0000 lumens.  And you can buy a setup with an air coolable hood for about $150.  If you add the number of bulbs and reflectors to get to 3000 lumens and 5000 lumens, it is probably going to run around the cost of a HID setup--those 42W CFLs are not cheap.


----------



## emrldthumb (Feb 4, 2015)

I wasn't suggesting I would try to light that whole space with CFLs or choosing between upgrading and not upgrading my lights. I just was trying to calculate how much hotter (the number) a 400w HPS would be compared to my current setup. I realize a can't use CFLs for that whole space, that's why I'm buying the new light. 

But I was hoping for a mathematical formula that calculates relative heat output of different lights so I could decide if it's worth buying a light now if I won't be able to afford a decent exhaust fan until sometime in spring.  If the 400w HPS puts out 50% more heat than my 300w CFLs then I think the exhaust would be up to the task at least until ambient temperatures rise a bit more. If it puts out 150% the heat, I might as well not upgrade the lights until I can afford the centrifugal fan too.

Clearer?


----------



## emrldthumb (Feb 4, 2015)

And in case I wasn't clear, I won't be adding the second container for a few more weeks anyhow, and right now I have almost 7500 lumens per square foot. So more than adequate for the one container.  I was hoping to put in the HPS at the same time as the second container and then upgrade exhaust a month or two later in time for late spring warmth.


----------

