On 11/08/2014 11:29 AM, Dave Cole wrote: >>> I wonder how long it takes to pay back the $75 > difference at 9 watts? > > 9 watts x 2000 hrs per year = 18KWHR/yr @ $0.10 per KWHR that would > be $1.80 per year so a payback of $75/$1.8 = $41.6 years > > I made up my own LED retrofits, because I couldn't find anything that looked like it would work well. I bought Cree 1W LEDs, and put a string of 20 of them on strips of PC board material with little grooves cutting the copper path. Each LED has 2 square inches of copper as a heat sink. I used commercial LED lighting regulators, which were pretty expensive. I have these in the kitchen, where they are on a LOT of the day. One strip of 20 LEDs is brighter than 2 32 W 48" fluorescents. Not only looks brighter, but my photometer also says they are brighter. I have them suspended inside the drop ceiling dual fluorescent fixtures with 2 x 4' plastic diffusers that were there before.
I measured the power draw of the old magnetic ballast, it was 103 W with a real power meter. The new system reads 21 W. I guesstimate payback in about 3 years. I first did a 10 W unit with a power supply I made myself, it has been running about 18 months so far, and is still working really well, too. I think if you use good LEDs at reasonable current levels, the dimming over time will be very slow. Cree has lifetime charts that show several hundred K hours before significant loss of brightness. I did make sure the LEDs run pretty cool, much cooler than a lot of the stuff sold in stores. Jon ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
