It's not just about cost of the bulb, how do you dispose of your bulb? do you take them to some hazardous waste site or just toss them in the trash and they end up broken in some landfill? what happens if everyone everywhere uses everything to 1/4 of its life then tosses it? Probably be more of a polluted up world than it is right now eh?
the few bulbs growers dispose is negligible in all actuality...what about the thousands from warehouses? think companies will spend the money for proper disposal? NOT...
the only way to know and not guess is with an ACCURATE light meter...which are not that expensive...$100 or so...same as those overrated hortilux hype bulbs
[TABLE="align: center"]
[TR]
[TD]HIGH ACCURACY LIGHT METER, Model : 1335
Model : 1335[/TD]
[/TR]
[/TABLE]
[TABLE="width: 750"]
[TR]
[TD="colspan: 2"]Specifications
[/TD]
[/TR]
[TR]
[TD]Display
[/TD]
[TD]3-3/4 Digit (4000 count) LCD Display
[/TD]
[/TR]
[TR]
[TD]Measurement Range
[/TD]
[TD]Lux: 40, 400, 4000, 40000, 400,000
F.C.: 40, 400, 4000, 40000
[/TD]
[/TR]
[TR]
[TD]Resolution
[/TD]
[TD]0.01Lux
[/TD]
[/TR]
[TR]
[TD]Accuracy
[/TD]
[TD]+/- 3% reading +/-0.5% F.S.
[/TD]
[/TR]
[TR]
[TD]Photosensor
[/TD]
[TD]Precision Silcon Photodiode
[/TD]
[/TR]
[TR]
[TD]Operating Temp.
[/TD]
[TD]0-50°C
[/TD]
[/TR]
[TR]
[TD]Operating Humidity
[/TD]
[TD]<80%R.H.
[/TD]
[/TR]
[TR]
[TD]Power Source
[/TD]
[TD](6) AAA Batteries
[/TD]
[/TR]
[TR]
[TD]Battery Life (typical)
[/TD]
[TD]200 Hrs.
[/TD]
[/TR]
[TR]
[TD]Dimensions
[/TD]
[TD]5.9(L) x 2.8(W) x 1.4(H)
[/TD]
[/TR]
[TR]
[TD]Weight
[/TD]
[TD]8.3oz (235 grams)
[/TD]
[/TR]
[TR]
[TD]Accessories
[/TD]
[TD]Carrying Case, Instruction Manual, Batteries
[/TD]
[/TR]
[/TABLE]
http://www.dasdistribution.com/products/lm-high_accuracy_models.htm#UV