Lamp wattage for 4 plants max.

Lighting doesn't depend so much on the number of plants, but more of the area light
needs to cover. How big is your grow area? Are you going to have a separate room
for vegging and one for flowering?

A 400W HPS or MH light will cover 4-5 square feet nicely.

I presume you are talking about using a HPS system? Or are you going with CFLs,
or LED lights?

Details Please

~Experimentalist

 

How much do you want to produce? Gettting 125 grams from a 250w hps or 200 grams from a 400w light per harvest is a realistic number for a semi-skilled grower. Alot depends on your skill level and technique but .5 grams per watt is a pretty good goal to set for the first couple grows. IMO Much Love.

 

The general rule of thumb is 40W per Sq Ft. The number of plants you grow depends on the size of the room and what strain you plan on growing. If you are planing on 4 plants max you will want to give ea. plant room, so you would want at least 12 sq ft min. 12 X 40 = 480W. A 400W w/ some CFL's or Flouros to make up the difference would be fine.

less

 

I would say it depends on the footprint that you want to light, not literally the size of the room. If you keep those 4 plants close together directly under the light, the room could be huge and they would still get most of the light (they would not get reflected light off the walls).

Perhaps even more importantly, though, is the distance from the light to the plants. Light intensity diminishes by the inverse square of the distance -- what that means is if you move the light twice as far away then the light intensity dimishes to one-fourth. So, if the plants are close together or spread apart, if they are in a big room or a small cabinet, if the light is too far away it won't matter.