Long narrow closets
Shape
1 to 2 ft wide and 6 to 10 ft (1.8 to 3 m) long
400 W HID
covers about 8 sq ft (0.75 sq m), such as 1 by 8 ft or 2 by 4 ft, on a fast shuttle
600 W HID
covers about 12 to 15 sq ft (1 to 1.4 sq m), such as 2 by 6 ft or 3 by 5 ft
1000 W or two 600 W
covers about 16 to 20 sq ft (1.5 to 1.9 sq m), such as 2 by 8 ft or 3 by 6 ft
Fluorescent narrow beds
Best tubes
T5 HO or CFL beat old household fluorescents for intensity
Target
50 to 70 W per sq ft (535 to 750 W per sq m)
1 by 4 ft bed
four 56 W T5 HO tubes, or four 55 W CFLs
Stay close
tubes only work if they sit near the canopy
The 4 by 4 ft closet
Area
16 sq ft (1.5 sq m), a strong personal-use size
Build bonus
plywood and plasterboard already come in 4 by 8 ft sheets
One 1000 W HID
about 62 W per sq ft (667 W per sq m)
Lower power
a 600 W or 750 W HPS is more efficient and still makes a bright, high-grade canopy (about 90,000 and 105,000 lm)
400 W
about 50,000 lm; buds stay decent but smaller and milder as light drops
Direct ratio
yield falls in step with the light the plants actually get
Hang and bounce the lamp
Reflector
choose one that aims light down onto the plants
Walls
white paint or reflective film around the perimeter
Adjustable hang
chain, pulley, or a locking yo-yo so you can raise the lamp as plants grow
Veg dark
plants do not need night in veg; a timer is optional until flower
Short blackout
up to about 4 hours off at a time will not flip them; longer gaps should be broken with light