The U.S. Department of Energy's CALiPER program has released Report 22.1, which is part of a series of investigations on LED MR16 lamps. Report 22 investigated the photometric performance of 27 LED MR16 lamps compared to benchmark halogens. Report 22.1 examines the photoelectric performance of that same set of lamps, using commercially available transformers and dimmers, as well as laboratory power supplies providing either AC or DC.
 
Five different test scenarios were used in the new study: 

 1.Electronic/ELV – Operation of each lamp model with an electronic transformer selected from the lamp's compatibility list (if available), and an electronic low-voltage (ELV) dimmer. The goal was to specify a system where the lamp, transformer, and dimmer were all listed as compatible, but limited available information often made this difficult.
 2.Electronic/INC – Operation of each lamp model with an electronic transformer and a typical incandescent dimmer. The transformer was listed as compatible with the dimmer.
 3.Magnetic/MLV – Operation of each lamp model with a typical magnetic transformer and a magnetic low-voltage (MLV) dimmer. The transformer and dimmer were considered compatible.
 4.AC Supply – Operation of each lamp model using a laboratory power supply delivering RMS (root-mean-square) 12V AC.
 5.DC Supply – Operation of each lamp model using a laboratory power supply delivering 12V DC.
 
The results demonstrated substantial variation in the performance of LED MR16 lamps, both within one test scenario and across multiple scenarios. The data also demonstrated the value of compatibility lists provided by manufacturers, the difficulty of retrofitting LED lamps into an existing system intended for use with halogen lamps, the relative stability of systems including a magnetic transformer (but potentially reduced performance in some aspects, such as system efficacy), and the possibility of generating misleading performance data when testing is performed with laboratory power supplies.
 
For a closer look at the findings, download the full report.