CFL's...

PROS:

Cheap energy cost
Lower heat
Plant can be within inches of light
Provides shorter stem growth
Can be perfect temps (kelvin 6400) for veg growth.

CONS:

Easy to buy shitty lights
Works best on smaller grows
Can be expensive up front cost
Lots of cheapo units out there to fool you
Gernerally need a fan for each light or two


HPS:

PROS:

Most efficient light per watt
Perfect flower temps (2500-2700K)
Most closely simulates sunlight for flower
Can grow large lots with fewer lights because comes in High wattage.


CONS:

Not ideal for vegging temps (want 6400K)
Can be expensive inital setup
contains no UV Rays
can create high temp problems



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