# PC WPG = Standard WPG?



## imatrout (May 12, 2005)

I have a question regarding PC flourescent lights in the context of WPG ratings. Does 3 WPG pf PC lighting equal 3 WPG of standard flourescent lighting?

In other words, my 2.7 WPG is typically quoted as "Moderate or Medium" light, but my lights are power compacts (PC). It seems that I should think about it as a higher WPG given all the rating info I've read is based on standard Flour. lights. Is that the right way for me to look at it?


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## trenac (Jul 16, 2004)

Yes, the WPG rule is based on standared flourescent bulbs. So you will have more WPG if using PC bulbs, by how much I'm not sure.


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## MatPat (Mar 22, 2004)

I think the WPG rule dates back to when normal output flourescents (T-12 shoplights) were what was available to most hobbyists. Wattage is not a very good way to measure light output since it actually measures power consumed, not light intensity (lumens). 

Since PC's, T-5's, HO, VHO, T-8's, and ODNO lighting have greater output (lumens) than normal output T-12 flourescent lighting, I don't think this rule really applies much anymore, though it is still commonly used. 

Here is some info I received via e-mail for a couple of 48" lights I was considering in the past. Note the difference in watts per lumens:

Sylvania Sun Stick (T-12, 40w), 5000K, 1892 lumens, 90 CRI, 47.3 lumens per watt
Coralife Nutri Grow (T-8, 36w), 5000K, 2800 lumens, 92 CRI, 77.7 lumens per watt

As you can see there is quite a bit of difference between the two lights in actual output!

I think 2wpg of CF lighting is enough to grow most plants. You may get faster growth with more lighting but your chance for errors (algae, stunting plants) happens much faster also.


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## shalu (Oct 1, 2004)

MatPat said:


> Note the difference in watts per lumens:
> 
> Sylvania Sun Stick (T-12, 40w), 5000K, 1892 lumens, 90 CRI, 47.3 watts per lumen
> Coralife Nutri Grow (T-8, 36w), 5000K, 2800 lumens, 92 CRI, 77.7 watts per lumen


You actually meant lumens per watt


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## MatPat (Mar 22, 2004)

I did mean lumens per watt and it is corrected. Thanks for pointing that one out Shalu


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## gnatster (Mar 6, 2004)

A more effective measurement would be Lumens per Square Inch of tank surface area, but you want stand there in the lfs and figure that one out?


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## imatrout (May 12, 2005)

Thanks to all for the responses. I have 4X96 watt of PC lights over a 150 gallon tank, roughly 2.7 wpg, buttttt since it's PC lighting it's really much higher equivalent and I should be able to grow any "high light" plant? Right?


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## freshreef (May 14, 2004)

lumen is a measure that is conected to the humen eye. plants dont "lumen" - grow-lux bulbs has much less lumen per watt (comparing to regular day light bulbs) and are much better "seen" by human eye.
anyway - i use t5 and can c that each t5 watt is much greater than t8 watt - can tell that by looking on the very demanding plants who need very high intensity .


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