High Intensity Discharge (HID) Lamps

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Introduction

High Intensity Discharge (HID) lamps produce a large amount of light in a small package with less power compared to incandescent and some fluorescent sources. According to the U.S. Department of Energy's Energy Efficiency and Renewable Energy (DOE EERE) office, lighting accounts for 20% to 25% of all electricity consumed in the United States. While an average household dedicates 5% to 10% of its energy budget to lighting, commercial establishments consume 20% to 30% of their total energy just for lighting. In a typical commercial or residential lighting installation, 50% or more of the energy is wasted by obsolete equipment, inadequate maintenance or inefficient use.

HID lamps and fixtures can save 75% to 90% of electricity when they replace incandescent lamps and fixtures. And, significant energy savings are also possible by replacing old mercury vapor lamps with newer metal halide or high-pressure sodium lamps.

Technology Options

High Intensity Discharge (HID) lamps produce light by striking an electrical arc across tungsten electrodes housed inside a specially designed inner glass tube. This tube is filled with gas and/or metal halides.

The three most common types of HID lamps are mercury vapor, metal halide and high-pressure sodium. HID lamps are commonly used for environments such as street lighting, gymnasiums and arenas. More recently, HID lamps — particularly metal halide lamps — have been used in small retail and residential environments as well.

HID lighting systems are being used more and more for two reasons: longer bulb life and greater energy efficiency. Longer bulb life results in lower maintenance costs. Greater energy efficiency, simply stated, means more light output (lumens) per watt of energy input.

Consider this comparison between incandescent bulbs and HID bulbs. An incandescent bulb that consumes 575 watts provides 10,000 lumens and has a lifespan of 1,200 hours, while a metal halide lamp at 400 watts provides 32,000 lumens and has a lamp life of 10,500 hours. A high-pressure sodium HID bulb of 400 watts consumption provides 42,000 lumens with a life of 6,000 hours.

Lighting Technology Lumen output Wattage Lumen/watt Life
Incandescent 10,000 575 17 1,200
Metal Halide 32,000 400 80 10,500
High Pressure Sodium 42,000 400 105 6,000

HID lamps require a ballast to start and to maintain their operation. The ballast in an HID lighting system generally has two purposes. It provides the proper starting voltage to strike and maintain the arc, and it regulates the proper current to the lamp once the arc is established. There are numerous ballast types designed for use with HID lamps, each offering different advantages and drawbacks. Recently, electronic ballasts have been used with lower watt HID lamps (35W to100W MH). These ballasts provide an electricity savings over magnetic ballasts of 8% to 20%. They also have the advantage of lighter weight, which can be important in some applications, such as track lighting. For further energy savings and light output control, this technology can be used with multi-step or continuous dimming control gear.

Resources for helping you consider HID lighting equipment include:

Efficiency Benefits

Lighting energy savings are realized over time and can be significant enough to not only pay for the new equipment, but also produce a return on the investment. While manufacturers and professional lighting managers have software that calculates the economic benefits of an upgrade, it pays to understand the principles.

HID lighting has several advantages over conventional halogen primary lights:

  • Higher light output. Three to six times the halogen's efficiency and roughly six to eight times an incandescent lamp's efficiency.
  • Whiter light. Very high color-rendering indices.
  • Longer service life. Lasts three to five times as long as a incandescent bulb.
  • Choices in controls and adjustability.
  • Lighter weight and compact size.

The following table illustrates an example of HID lamp savings, which require fewer input watts per fixture for comparable light output. Lighting System A is the existing incandescent system and Lighting System B is a proposed retrofit system using more energy efficient lamps and ballasts.

  Lighting System A Lighting System B
Input Watts/Fixture 175 100
Hours of Operation/Year 3,000 3,000
Electricity Consumption/Year (kWh) 525 kWh 300 kWh
Electricity Savings/Year (kWh) --- 225 kWh
Utility Cost/kWh $ 0.10 $ 0.10
Electricity Savings/Year ($) --- $22.50
Number of Fixtures Retrofitted 100 100
Total Electricity Savings/Year ($) --- $2,250

Note that additional energy savings can be calculated from the reduced air conditioning load, resulting from less heat produced by the lighting system. Lighting systems convert only a fraction of their electrical input into useful light output. Most of the energy is released directly as heat into the space. Hence, any upgrade of the lighting system that reduces the input wattage reduces the air-cooling system load and thereby brings additional energy savings.

Payback is a simple way to perform an economic analysis. If the initial cost of the lamps and ballasts (including the cost of the components and labor) is about $70/fixture or $7,000 total, and the energy savings are $2,250 per year, simple payback is: $7,000 / $2,250 = 3.1 years. Note that other initial costs may include financing, consulting fees, tax effects and waste disposal.

Manufacturers

There is a broad range of HID lighting manufacturers across all sectors, including:

Lighting EZ Search from Thomas Publishing features a database of manufacturers of lights, lamps and lighting equipment.

The Lighting Newswire features a list of manufacturers.

Purchasing Tips

When comparing HID lamps to standard-output lamps, initial costs may be higher but electricity savings are approximately 15% to 25%, and fewer fixtures may be required when you take into account higher lighting output. Additionally, HID electronic ballasts can be more than double the cost of their magnetic counterparts. However, manufacturers have introduced electronic ballast/lamp systems that are more comparable in costs to the magnetic systems.

The basic factors that go into specifying a HID light source and a fixture include:

  • Ballast requirements
  • Ambient temperature
  • Size
  • Lumen needs
  • Color temperatures and color rendering abilities
  • Service life
  • Line voltage variations, possible line voltage drops and circuits sized for high starting current requirements must be considered.

Another source for specifying and buying lighting is LightSearch.com from inter.Light, Inc.

Finally, consulting a lighting professional is the best way to ensure proper lighting performance and minimize energy expenses.

Emerging Technology

Recently, lamp manufacturers have introduced colored metal halide lamps. This coloring is achieved by using a single element metal in the arc tube to produce emitted colors such as blue, green, pink and yellow. No colored phosphor or filter is used or required.