So I was flipping through a magazine the other day, and came across a great article on the “Relative Efficiency of Light Bulbs.”  We love hydroponics, but we’re always looking for information and ways of making hydroponics “greener” than it already is.  We started manufacturing Top Feed Systems for this very reason.  It has really cut down on our energy costs, which in turn helps the environment.  Anyway, back to lighting.  So it all comes down to lumens — measure of light intensity hitting a surface.  Household bulbs are measured in Watts, but when growing we care about Lumens (and lumens give us the most bang for our buck).  So they compared 6 types of light bulbs; incandescent, mercury, fluorescent, fusion sulphur, metal halide and high pressure sodium (HPS).  The 100 watt incandescent bulb shining 1 foot away from an object will put roughly 175 lumens, but 100 watt mercury will produce 600 lumens.  Put a 100 watt HPS bulb in the same circumstances and we’re talking 1,400 lumens.  So in conclusion High Intensity Discharge bulbs may cost more, but you’re getting a lot more bang for your buck and your plants will appreciate you more.  Lastly, here is the relative efficiency for the 6 bulbs types I mentioned above.  Incandescent: 8% efficiency; Mercury: 29% efficiency; Fluorescent: 38% efficiency; Fusion Sulphur: 44% efficiency; Metal Halid: 45-57% efficiency; and the big winner, High Pressure Sodium: 64% efficiency.

Original Source: How to Supercharge Your Garden