HID - General Lighting Upgrade

Although most industrial facilities have upgraded their HID lighting systems in recent years, many older industrial facilities may still use mercury vapor lighting. Mercury vapor is the least efficient of all the HID sources and thus should be changed out to either metal halide or high pressure sodium. Generally, high pressure sodium is the best source but there may be some occasions where color properties are important and thus metal halide lamps should be used. Light from high pressure sodium lamps has a characteristic golden color while metal halide lamps produce a crisp white light. However, high pressure sodium lamps are now available with improved color properties. They should be considered very carefully. In general, when changing sources, you will also need to replace the ballasts.

Energy savings
To help you compute the energy saving potential for changing out a less efficient lighting system for a more efficient one, use these equations:

• Demand Savings = Current fixture wattage - New fixture wattage x Number of Fixtures

  Demand Savings = _____watts - _____watts x _____fixtures = _____kW

• Energy Savings = Demand Savings times annual operating hours

  Energy Savings = _____kW x _____hrs of operation = _____kWh

• Demand Cost Savings = Demand Savings x $/kW Demand Charge x 12 months/year

  Demand Cost Savings = _____ kW x $_____/kW x 12 months/year = $____

• Energy Cost Savings = Annual energy savings x $/kWh

  Energy Cost Savings = _____kWh x $_____/kWh = $_____

• Total Savings = Demand Cost Savings + Energy Cost Savings

If you are unsure of your current demand and energy consumption charges, refer to your utility bill or contact your utility company representative.

The costs for installing this type of retrofit will vary. Equipment and labor costs for installation should both be considered. Once you know these costs you may evaluate the attractiveness of the project using any of the normal financial measures. Simple payback is probably the most common. This type of analysis will apply to most situations. Your operating hours and energy costs may be different but the calculations used in this example will still apply.

Advantages
The main advantage of this retrofit is obviously the energy savings. In addition, high pressure sodium has a much better lumen maintenance than mercury vapor lamps. The lumen output for mercury vapor lamps continuously decline; such that, at the end of their rated life, they only deliver about 50% of their initial rated light output. High pressure sodium lamps lose only about 20% of their light.