Efficiency Advice

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Jun 6, 2006
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Sacramento, CA. Outside w/ Southeast Exposure
What's the more efficient light source?

400W MH on a 6' light track

or, 8 150W compact (coiled) flourescents???

If the 400W MH was used, plants would be table top or ledge top (horizontal space). If the CFLs were used it would be on a two tiered shelf, and I'm concerned that the space would be too small for the large multis.
i ain't entirely sure but it seems that the mh at 400 watts would use less energy than 8 x 150 watts which would be 1200 watts.
only thing is that i thought mh was not as good for flowering as for vegetative growth. i also think, but an unsure, that the mh will give stronger, more intense light than the cfl's...
Hi Heather:
I use the 400 W MH. The good thing about these is you get more light out of the bulb, better for higher light plants. The new elctronic ballast are also very efficient compared to the older design. I have replaced all my flourescents with 400W, some are on movers. I believe that you will find that the 400W is much more efficient and also more effective for high light plants.

How much energy does the 400w light track consume?
Does the track move with a motor?
Is 400w the total power consumption of the light track?

To figure which is most efficient you will want to consider how much area each will light, how many hours each will need to be on, and the cost per hour depreciation on the tubes.

If your question is which will cost less to run then total watts gives you that answer.
Heather said:
Thanks to you both. I wasn't sure if it was as simple as just counting up the wattage but it seemed to me that I had read something about MH being more efficient in the long run.

Now I just need to get Rob to ship me that light rail. :poke:

Don't forget to figure in the cost of shipping the light rail! :evil:

I think there is actually more involved than just rated watts. Things like how much extra energy is used to start up. For example an electric motor uses a lot of energy just to get up to speed and that energy used is not included in the rated "watts" of the motor, but you pay for it.
I don't know if the HID light track uses extra energy to turn on?
I'm just trying to confuse you.
gonewild said:
I'm just trying to confuse you.

Good job. :)

Seriously, I just wondered which would be the preferred choice when I move the plants back to my mom's basement. I have both but won't have enough plants to need both. I am leaning towards the MH (since I think it is also better for plant growth). It will certainly be less wattage to run than the CFLs.
I think likespaphs is right; in overall enery cost, the CFLs will cost more, but I don't know whether you'll be getting more candlefeet with them... you might. If that were the case, you might be able to use the CFLs for fewer hours per day, which would probably make a difference... but it would obviously have to be a pretty dramatic time difference (about 1/4).

I'd check out the light output... standard household CFLs are actually much lower wattage (15W or so to replace a 100W standard bulb). A 150W CFL would be a floodlight (like the flourex lights), and I doubt that you'd need anything like 8 of them.

- Matt
Hm, I'll have to check that, maybe I have 150W equivalent CFLs. They look like the 42 W. if you do a google search, they aren't the big growing CFLs with the reflector (that looks more like my MH set up).

The way I use them currently is on a two-shelf cart. Each shelf fits three humidity trays, and I have 4 bulbs, one in each corner (I only have plants on the top shelf right now). My main concern if I went this route is that all of my plants are likely not going to fit well on the two shelves (blame those big multis I like so much!). So, going with the plants on a flat surface with the MH light above on a track (that moves) seems like a better plan, especially if it is more cost efficient.
If you take a look at the base of the CFL bulb, on the ballast it will tell you exactly how much energy it uses. I have a little guy here on my desk to replace a 60W in my desk-lamp that says: Helical 10W, 120VAC, 60Hz 140mA .

A 150 W CFL would be pretty serious. Here's a 65W floodlight that claims to be as bright as a 500W standard floodlight, for example: http://cgi.ebay.com/Fluorex-Flood-L...DVWQQrdZ1QQcmdZViewItem?hash=item160090739572

Ahh... here's a 150W. Two of these would probably beat a 400W metal halide, and would still be less energy. http://cgi.ebay.com/Complete-Sun-Sy...DVWQQrdZ1QQcmdZViewItem?hash=item270094317046

Anyway, this is all just to say that I think the energy calculations up to now might not be accurate.

- Matt

Incidentally, I think that the power-up energy use for CFLs and Metal Halide would be about equivalent; they both have ballasts that need to soak some energy before powering the bulb, but considering the amount of time per day that the lights will be powered on, I don't think that any differences in this area will make a significant difference in operating price.
I have a 100w equivalent that actually uses something like 20w of energy.
My light meter reads 700 foot candles about 12" below it.
If you are talking about using those bulbs then 8 of them would be cheaper to run than the HID.
gonewild said:
I have a 100w equivalent that actually uses something like 20w of energy.
My light meter reads 700 foot candles about 12" below it.
If you are talking about using those bulbs then 8 of them would be cheaper to run than the HID.

Problem is are they bright enough to bloom my plants? The Phrags have been doing okay under them (about 12") and blooming well but I seriously doubt I could bloom a roth. Additionally they've always been supplemental as the plants have gotten some natural light. They won't be getting natural light at all when I move.
IN that case, if they are in the 35-42W range of energy use, you'll be using more like 280-336W per hour with them, as opposed to 400, which is a pretty significant difference. I'm not sure how that 15,200 lumens compares with a 400W Metal halide, though. You'll have to compare how long you'll have to leave them on to get the same amount of energy to the plants.

I see that some metal halide bulbs are claiming as much as 36,000 lumens output. However, since you're going to have it on a track, only a fraction of that light will get to any particular plant (less light while the light is at the other end of the track)... so, its hard to make a direct comparison.

- Matt
Well, moving beyond efficiency to light quality is a different issue... I don't know what spectrums the CFL are strong in, and there are lots of different spectrum MHs available. CFLs that are made for plants may have fewer lumens in total output, but their lumens are in a range that the plant can use, and are therefore more useful (in theory) than brighter lights of other spectrums.

I have heard of people blooming roths under standard fluorescents, so I imagine CFLs would be possible. Easy? I don't know.

- Matt
Heather, the most efficient solution would be to just send all the plants to me...
Are you actually going to leave the roths in one place long enough make a difference? :poke:

Let me rephrase that question.. Do you plan on this setup to be permanent?

I think the compacts as a constant might be even better than the roving HID based on what Matt has said.

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