Grow Box Lighting Calculation: Practical Examples

In addition to the main article on lighting, here are some examples of area, power, and lamp type ratios for grow boxes. For healthy plant growth, you need at least a 50-watt HPS lamp for an area of 12 x 12 inches (0.09 sq. m). A plant can also grow under a 20-watt CFL, but it will develop slowly, and the lack of light will significantly reduce the yield.

• HPS 70W – CFL 100W – LED 50W – 12 x 12 in (0.09 sq. m)
• HPS 100W – CFL 150W – LED 70W – 16 x 16 in (0.16 sq. m)
• HPS 150W – CFL 250W – LED 115W – 20 x 20 in (0.25 sq. m)
• HPS 250W – CFL 400W – LED 180W – 24 x 24 in (0.36 sq. m)
• HPS 400W – LED 360W – 36 x 36 in (0.8 sq. m)
• HPS 600W – LED 530W – 43 x 43 in (1.2 sq. m)
• HPS 1000W – LED 750W – 51 x 51 in (1.7 sq. m)

The optimal area for comfortable plant development is about 0.36 sq. m (if you’re not doing micro-growing in a computer case, of course!).

It’s important to consider whether a particular lamp can be used depending on your grow box’s ventilation system. I’ll cover this topic in more detail later.