What is Watts per gallon.

Rex Grigg · Joined: 16 Aug 2007 Posts: 14

On Sat, 28 Jun 2003 09:18:13 +1000, "Graham Broadbridge" peachy dot org> wrote:

When planted tank people talk watts per gallon we are referring to
fluorescent watts.

>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.
>

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Chuck Gadd · Joined: 16 Aug 2007 Posts: 37

On Sat, 28 Jun 2003 09:18:13 +1000, "Graham Broadbridge" peachy dot org> wrote:

>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.

It's not just the spectrum that is the difference.

Most of the energy of an incandescent light is turned into heat, not
light.

Most of the energy of a fluorescent light is turned into light.

Watts per gallon only applies to high-effiency lighting, such as
Fluorescent and Metal Halide.

Chuck Gadd
http://www.csd.net/~cgadd/aqua

Graham Broadbridge · Joined: 16 Aug 2007 Posts: 23

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.

Robert H · Joined: 16 Aug 2007 Posts: 3

"Graham Broadbridge" wrote in message news:...
> 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