"Graham Broadbridge" graham at peachy dot org wrote in message . au...
What is watts per gallon?

If I have 2 x 100 watt incandescent that is 200 watts.

If I have 2 x 38 watt flourescent tubes that is 76 watts.

The flourescent tubes output much more light in the correct spectrum.
Shouldn't we be measuring the light level at the required wavelength rather
than just measuring the input power required by the illumination source?

Even forgetting the wavelength, surely we should be measuring foot-candles
or lumens rather than watts?


Graham.

"Watts per gallon" is just a general rule of thumb for estimating the
intensity of light needed to grow plants. It is based on the average
lumen output per watt of flourescents. Flourescents put out something
like 4 to 5 times as much light per watt as a incadescent. So you
would need 4 or 5 times as many incadescent bulbs to equal the same
amount of light as one flourescent...somewhere in that range.
Professional hydroponic growers and even greenhouse growers use
basically the same formula. Indoor hydroponics use Metal Halides
mostly, or high pressure sodium, even for house plants. Greenhouses
use Metal Halides on cloudy days or for areas that do not get enough
sun. The only time incadescents, including flood lamps, are used is
for sprouting seeds when the light is only inches above it.

Robert
aquabotanic.com