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LEDs do indeed have advantage for highly directional lights. For example, in the consumer product range, many manufacturers offer R-xx shaped LED screw-in accempt lamps. The focused, narrow beam produces theatre spotlight like beam good for decorative use, but for disperse and indirect lighting, LEDs don't have any inherent advantage.There are far more inappropriate LED installations than there are justifiable ones. New technology and new gadgets seem to get attention in that way. Being a lighting designer first, I can be the LED's strongest opponent.
That being 'said', there are a few factors that should follow. There are several luminaire types that can benefit with LEDs and really save up to 50% in energy consumption today, even before LED efficacy is raised any more.
When the IES photometric file shows a bulb fixture to be 65% efficient, that is a prime application for LEDs. A properly designed LED fixture can usually get 90% of its light out of the fixture and onto the target.
We have replaced a few 175W MH post-top globe fixtures with 80W LED retrofits that actually had higher foot candle readings than the original light source.
But a word of caution - energy savings alone doesn't make the ROI justifiable. The reduced maintenance is essential to make the day with LEDs. Use an ROI calculator before going down the LED path!
There are fluorescent fixtures with 80+ % efficiency. Not all of it is directed straight down, but allowed to scatter and spill out the top, t hen bounce off the ceiling so you'll have semi-indirect lighting that's desirable for indoor lighting.
When you said 80W LED replaced 175W MH and foot candle readings were higher, where were you making the measurements? How old was the metal halide fixture and do you suppose the cutting edge metal halide fixture using a lower wattage lamp and a compact ceramic MH(that allows better control using optics) and advanced optics to have better result than before or are you going to credit LEDs for improvement?
Top tier LEDs maintain output better than the average MH, HPS maintains lumens better than LEDs. LEDs maintain 70% in 50,000 hours, while HPS maintains 80-90% before reaching end-of-life at 30,000 hours and more or less ambient independent. After allowing for LEDs higher depreciation and adverse impact from high ambient, a lower output HPS can be used to maintain the 70% of what LEDs would put up new.
output checks on new install, of course, compares non-depreciated LEDs to HPS or MH that's been depreciated.