help me check my math, new to this

Ok so I've got a 4'x1.5' area that I plan to grow in and I want to make sure that my math here is correct.

4x1.5=6 sq. feet....6 square feet will need around 60,000 lumens ....and at about 65 lumens per watt that is a little over 920 watts

does this sound a little extreme to anyone else or did is my math looking good on this one.

willgood said:

Ok so I've got a 4'x1.5' area that I plan to grow in and I want to make sure that my math here is correct.

4x1.5=6 sq. feet....6 square feet will need around 60,000 lumens ....and at about 65 lumens per watt that is a little over 920 watts

does this sound a little extreme to anyone else or did is my math looking good on this one.

Click to expand...

im not sure where you are getting the lumens per watt ratio i think you are basing it on 42 watt bulbs.... each bulb is different and the wattage rating will change the lumens/per watt ratio with each bulb. the sun produces about 10,000 lumens per sq ft, so there you are correct. to produce this amount of lighting you are going to need roughly 22 42w ( 2700 lumens ) bulbs or 35 23w ( 1700 lumens ) bulbs. With your situation the 23watt bulbs are going to be more efficient : 23w x 35 = 805watts of power ; 42w x 22 = 924watts of power : each with an equal amount of lumens produced.

hope that helps you a little. good luck with your grow!

I'd say your math is about right.

60,000 lumens / 2,800 lumens per 42W bulb = 21 42W bulbs

21 x 42W = 900 watts

Your math is right but your assumption on 6 sq ft might not be. Will the entire 6 sq ft be covered with grow or just the center of it? And more important, how close can you get the cfls? The only lumens that count are those that actually strike foliage. So even though you are generating 60k lumens, you never get them all to the leaves. The ability to get cfls and T5 flouros close to foliage, thereby increasing impact lumens, is why flouros used correctly can approach the efficiency of lighting that must be kept further back.