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Lumens per watt
OK, so it's not PAR. If you have PAR figures, please add them. Use a
fixed pitch font for best results in viewing.
Incandescent
Vlt Watt Lumens/watt (initial)
120 100 17
Quartz-halogen
12 5 10
10 11
20 15 (35 w/reflector)
35 40
120 20 14
35 17
50 16
100 20
Fluorescent T-12
120 80
Fluorescent T-8
120 90
Fluorescent T-5
120 75 (70 for multiple u-tubes)
Metal halide
120 any 85
Around here, power costs about $.40 per watt-year (based on 3000 hours on
time).
DIY fluorescent costs about $1/watt for nice looking, $.16/watt for a shop
light hanging from the ceiling on chains. Low-voltage halogens cost about
$.53/watt according to Tom Barr.
So per 1000 lumens (and remember, we should be talking about per PAR):
Buy Run($/year)
Incandescent 32 24 (either regular or quartz-halogen)
Fluorescent 11 5 (includes metal halides too, close enough)
I find it very hard to understand how anyone can argue for incandescent as
less costly.
Did I screw up one or more of the computations?
--
Dave Gomberg, San Francisco mailto:gomberg at wcf_com
http://www.wcf.com/wcf
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