Retrofitting With High Efficiency (HID) Lamps

The most efficient lighting sources available today are High Intensity Discharge (HID) and Low-Pressure Sodium (LPS) lamps. With the exception of one HID lamp (mercury vapor) HID and LPS lamps produce the most light per watt of any light source. They create up to one-third less heat and last as much as 24 times longer than incandescents. Most parking lots, shopping centers and sports arenas now use HID or LPS lamps, since they are especially useful for outdoor security lighting. They can also be considered for indoor use, particularly with ceilings 14 feet or higher.

Despite their advantages, these lamps do have some special considerations. Like fluorescents, they need special ballasts. They have a warm-up time of three to seven minutes and restrike time (the delay between off and back on again) of three to five minutes, making them inappropriate for certain indoor uses such as retail clothing or interior design sales.

High Intensity Discharge (HID)

HID lamps can be used in a variety of applications, depending on the situation. The three types of HID lamps are Mercury Vapor, Metal Halide and High-Pressure Sodium.

Mercury Vapor (MV) lamps are most frequently used outside for parking and security lighting. These lamps have a white or blue-white light and limited color rendition, but are still suitable for many outdoor uses. They are the least efficient of the HID lamps (slightly less than fluorescents) and should be replaced with more efficient metal halide or high-pressure sodium lamps when possible.

Metal Halide (MH) lamps provide the best color rendering of all HID lamps; color rendition is almost as full spectrum incandescents. They can be used for merchandise display, entry lighting, or in any situation where color rendition is important and are frequently used for outdoor security and sports lighting.

High-Pressure Sodium (HPS) lamps are the most efficient and economical of the commonly used HIDs. Because of their warm golden light and limited color rendering, they are more suitable for outdoor than indoor situations. They are most frequently used as security and outdoor lighting, or in indoor areas, such as warehouses, where color rendering is unimportant.

Low-Pressure Sodium

The low-pressure sodium (LPS) lamps are less commonly used. This lamp has a limited yellow tone that renders colors poorly. In addition, a broken LPS coming in contact with moisture could start a fire. LPS applications are limited to secure fixtures.

Replacement Opportunities

Replacement of Interior Mercury Vapor and Incandescent. Due to their low lighting efficiency, mercury vapor lamps should be replaced wherever possible. In areas where identifying colors is important, they should be replaced with metal halide fixtures; if color is not important, they should be replaced with high-pressure sodium fixtures.

Replacement of Exterior Incandescent and Mercury Vapor. Incandescent and mercury vapor lamps in exterior locations should be replaced with metal halide, high-pressure sodium and/or low-pressure sodium lamps. If color is important, metal halide lamps are a good option.

High-Pressure Sodium Screw-in Replacements. A high-pressure sodium screw-in or direct-wired adapter is available now for incandescent replacements. While the applications may be fairly limited (in storage areas, warehouses, building extensions and other areas where aesthetics are not important), these lamps can provide substantial energy savings. The restrike time is only about 30 seconds, which is not objectionable in most areas.

If You
Are Using
Watt Savings
per Lamp•
Annual $ Saved*
(10 Lamps)
Mercury Vapor      
100-Watt 50-Watt LPS
$  129
  35-Watts LPS
$  142
175-Watt 100-Watt HPS
$  153
  100-Watts MH
$  153
  90-Watts MH
$  175
250-Watt 150-Watt HPS
$  169
  175-Watts MH
$  147
  135-Watts LPS
$  217
400-Watt 250-Watt HPS
$  307
  250-Watts HPS
$  329
  135-Watts LPS
$  596
1,000-Watt 400-Watts HPS
Metal Halide      
100-Watt 70-Watts HPS
$   88
  55-Watts LPS
$  116
175-Watt 100-Watts HPS
$  164
  90-Watts LPS
$  186
250-Watt 1505-Watts HPS
$  219
  135-Watts LPS
$  267
400-Watt 250-Watts LPS
$  329
  155-Watts LPS
$  526
•Watt savings will not necessarily equal original lamp voltage minus new lamp wattage, due to differences in ballasts.
*Using $0.06 per kWh and 3,650 operating hours per year.