http://www.creatiesintechniek.nl/Led/test2.html
Theres the link, on that particular grow he gets 53g from just under 60w of light. I was a little off on the specs but still thats great, considering he was using soil as well. This is also a little old, you can get light even more powerful then those like the 3w versions I bought (his are 2w a piece) which not only are more powerful but more effective in supplying light.
right how long did he veg for? the proper way to to work out GPW (gram per watt) is the total power used through out the grow.
i.e
I have X ammount of cuttings and I veg them for 3 days under 110w CFL remember this!! because the amount of time in veg plays a lot in the final GPW
i then switch into flower 12/12 lets say 1000w for 8 weeks i flower 36 plants under the 1000w and each plant gives me 1oz per plant (pice of piss) thats 36 oz or 1000grams per 8 weeks cycle.
that is 1gpw over the space of 8 weeks or 125 grams a week. add the 3 days worth of veg time under 24/3 = 7.3KWH
total power used is 84 KWH per week 1000 watts per day = 12kw
total power used is 84 KWH per week
84KWH x 8 weeks = 672
now add the 7.3KWH from the veg time total watts used = 679.3 total KWH over the space of 8 weeks.
i.e #2
i veg 4 plants for 6 weeks under 400w scrog. that is a total of KWH per 67.2 KWH week or 403.2 over the 6 weeks im in veg 24/7
I now swith to my 1000w and go 12/12 for 8 weeks the same as above works out as 672 KWH now add the veg wattage to the flower and the total is = 1075.2 KWH but that has taken 14 weeks from start to finish lest say the scrog hits you 1000grams
this is where lots of people turn round and say i jet over a GPW and then you ask them how long did you veg for?? and they say 6 weeks that is not a GPW over the space of 8 weeks that is a gram per watt over 14 weeks.
there was a calculator on over grow years ago that would work out how efficant your grow was. the method used was the 8 week cycle because most plants finish in 8 weeks and then you would add the veg time and it would work out the total GPW over the 8 weeks including the veg to show your GPW as you can see the person who is growing scrog is not hitting noware near the GPW now his he.
the GPW is the total anount of time from start to finish not just the flowering time otherwise there would be no way to compare differant gardens in effectivness.