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Lamp/light source efficiencies

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The figures below are for the various efficiencies in terms of Lumens/W for different lamp types. The higher the Lm/W, the more efficient the light source. The data is based on web info for Philips lamps with the exception of SOX which is via Lamptech.

Note this doesn't tell the whole story as except for the LED lanterns, no control gear losses are included.

SOX gear is more lossy than SON. 35W SOX circuit loss is very similar to 50W SON. 135W SOX circuit loss is similar to 150W SON.


26W SOX-E: 141 (replaces 35W SOX)

35W SOX+: 130

35W SOX PSG: 126.3

36W SOX-E: 163 (replaces 55W SOX)

55/90W SOX: 120

66W SOX-E: 164 (replaces 90W SOX)

135W SOX: 135

180W SOX: 150


Directly interchangeable with SON

70-250W: 90


45W: 95

60-140W: 115

CDM Elite

As used by Highways Agency for Iridium retrofits on trunk roads

210W: 110

315W: 114

CDM Master

"traditional" CDM lamps

35-70W: 94

150W: 86


Fluorescent used in Surrey and south coast PFI for residential lighting

36W: 80.5

55W: 87


As in Philips BGP32X lanterns

59.1 (4200Lm, 48 LEDs)

84.4 (16800Lm, 160 LEDs)

SON Master PIA

70W: 94

100W: 107

150W: 116

250W: 133

400W: 141

600W: 150

With the exception of the 400/600W SON, SOX is still the most efficient discharge light source.

CDM-Elite/Cosmopolis are comparable in efficiency to the medium SON lamps, CDO-TT and CDM are the less efficient types of MH lamp.

PL-L is similar to "conventional" MH.