Lumens per watt-a non-scientific observation


I've been reading the debate over lumens, watts, MH vs FL, and thought a
little research was in order. In about 5 minutes, I came up with the
following table from data in Grainger's 385 (1994) catalog:

Ranked in order of efficiency (more lumens per watt):

6: 60 Watt Daylight (6500K) HO Flourescent T-12 (all FLs are 48")
Initial Lumens: 3600
Lumens per watt: 60

5: 110W Cool White (4100K) VHO FL T-12
Initial Lumens: 6950
Lumens per watt: 63.18

4: 40W DAylight (6500K) FL T-12
Initial Lumens: 2600
Lumens per watt: 65

3: 160W Daylight (6500K) VHO FL T-12 72" (the smallest Daylight VHO in the
Initial Lumens: 11300
Lumens per watt: 70.625

2: 175W Metal-Halide
Initial Lumens: 13000
Lumens per watt: 74.29

1: 32W TL-80 4100K FL T-8
Initial Lumens: 3050
Lumens per Watt: 89.0625

Outside of our purpose:
180W Low Pressure Sodium (LPS)
Inital Lumens: 33000
Lumens per watt: 183.33

So, it looks like the T-8s have it! Of course, getting enough of them over
a tank can be problematic. It also shows that watts per gallon or any other
reference that uses watts can be misleading, and is probably bordering on
useless (like the much misused and utterly useless 'candlepower'). Lumens
should be a more accurate measurement, and obviously the depth of the tank
is more significant than the capacity.

What surprised me was the inefficiency of the HO & VHO lamps. Of course,
they may be the only solution in getting an acceptable quantity of lumens
into the tank in some situations.

It would be interesting to determine how many lumens we are putting into
our tanks.

Larry West