Energy Reduction Applications: Lighting

Overview: Lighting typically consumes 25-35% of the total energy used in a facility, so it’s well worth looking for energy efficiencies in this area. Older lighting fixtures (see Lighting Types below) are grossly energy-inefficient and prone to substantial decay in light output over time, which means you probably have 30-40% less light now than you did when they were installed.

Productivity: Replacing older fixtures can yield significant energy savings as well as harder-to-measure, but nonetheless real, improvements in productivity. Often you don’t realize how bad the light has become until new lighting is installed. If you haven’t replaced your lights in the last 3 years or so, recent advances in lighting technology make it well worth your while revisiting the issue.

No single fixture or lighting system suits every purpose. As a result, the lighting industry has several hundred manufacturers of ballasts, bulbs, fixtures and controls distributing their products through a myriad of architects, engineers, lighting designers and lighting distributors.

Lighting Efficiency: The quality of light enjoyed by workers is critical. In a perfect world, you want:

• The best quantity and quality of light for the task at hand - delivered to the work surface
• The lowest total cost of ownership, which doesn’t necessarily mean the lowest initial cost

Total Cost of Ownership: Just like buying a car, initial cost is only part of the equation. Since ceiling heights can vary widely, often requiring use of a elevated platform, labor costs to replace burned-out lamps and ballasts can be substantial. The main components of TCO are:

• Initial cost: Typically 4-6% of annual cost of operation
• Energy efficiency: Especially dimmability – 85-90% of annual cost of operation
• Maintenance: Labor can be 8-12% of annual cost of operation
  • Lamp longevity: Ceiling temperature-dependent
  • Ballast longevity: Ceiling temperature-dependent
• A/C Load: Lower temperature lamps will reduce A/C load
• Disposal Costs: Certain lamps (e.g. HID) require specialized disposal

Payback: The good news is that, in many instances, it is possible to improve both light quality and energy consumption simultaneously, with rapid paybacks - frequently less than 2 years. Even better, in some states there are substantial incentives (grants and loans) that can reduce the capital cost and accelerate paybacks significantly.

Major Lighting Types: To provide detailed information on the hundreds of different types and brands of lighting would be far too large a task. Instead, here are some common-sense ways to evaluate lighting upgrades, as well as an outline of the major categories of lighting and their improvements in energy efficiency over the last few years.

A lighting product or ‘luminaire’ is a system, not a single item. The light output, quality and efficiency depend on how well all the elements of the system work together. These elements include:

• The fixture itself with a built-in reflector, which will determine the output and pattern of light
• The ballast - which may have some intelligence – dimming, communicating with building management systems etc
• The bulb or ‘lamp’, which will put out a certain number of lumens while using a certain number of watts
• Sensors which may be used for detecting daylight (i.e. less artificial light needed on bright days) or occupancy

Considerations for selecting the optimum lighting system include:

• Ceiling height
• Ceiling temperature
• The number and pattern of fixtures – which depends on:
  • the layout of the facility
  • the number and location of people working there
  • the tasks they perform
• Lamp life – which is critical because the labor cost for replacing burned out lamps is significantly greater than the cost of the lamp itself
• Installation – the design of the lighting system (which depends on activities in the facility e.g. offices, warehouse, manufacturing etc) will determine the spacing between fixtures and the cost of hanging them. This can amount to 30%+ of the initial cost

Major Lighting Categories - listed from oldest type to newest type:

• Sodium Vapor with magnetic ballasts
• Mercury Vapor with magnetic ballasts
• High Intensity Discharge - usually distinctive bell-shaped fixtures used for high ceilings, e.g. big box retailers, gymnasiums, stadiums and arenas, multi-story car parks, shopping malls etc.
  • Metal Halide – very bright (40,000 lumens) but requires 5-15 minutes to warm up, and output decays significantly over time (30-40%).
  • High Pressure Sodium - yellowish color light commonly used in parking lots
  • Both types can be retro-fitted with digital ballasts instead of magnetic coils (ballasts). This can save 20-30% of the energy consumed, or the entire fixture can be changed for a more modern fluorescent one.
• Fluorescent Lights
  • Older magnetic ballasts with T-12 lamps (1.5” diameter)
  • Newer electronic ballasts with T-8 or T-5 lamps (1” and 5/8” diameters)
    • Standard Frequency electronic ballasts
    • High Frequency electronic ballasts designed primarily for dimming
• Low voltage lighting & LED lighting are very energy-efficient but are only suitable currently for specialized applications

Energy savings will depend on:

• Wattage of bulbs
• Efficiency of ballasts
• Dimmability through occupancy or daylight sensing
• Hours of operation & cost per kWh
• Operating temperatures

Lighting Retrofits: As a general rule, switching from older lighting types - HIDs or T-12s - to newer T-8s or T-5s can save about 30%+ of the wattage used. There are other improvements, such as high-efficiency reflectors which can also improve performance. The following table outlines average savings you can expect from these upgrades.

Light Quality: Color Rendering Index: This is how the color of an object under a light fixture is perceived by the eye. Not all lamps will produce the same type of light. The CRI represents the ability of a lamp to render color accurately and to show color shade variations more clearly. High color rendition allows us to see objects, as we would expect them to appear under natural sunlight.

Below is an index of CRI which indicates which lamp will be the most natural-looking and have the least amount of color shift. It is rated on a scale of 0-100 with 100 being the best or most ‘natural, i.e. not too harsh and not too soft:

Color Temperature: A light bulb looks like a certain color because of the Color Temperature. It is not actually how hot the light is, but how the ‘radiator’ reaches a certain temperature to produce the color of the bulb. The ‘radiator’ will change color as the temperature increases from red to orange to yellow, white, blue-white and finally blue. A lamp with a low color temperature will have a "warm" appearance (red, orange, or yellow). Conversely, a lamp with a high color temperature will have a "cool" appearance (blue or blue-white). The scale goes from 1600 Kelvin (e.g. sunset red) to 20,000 Kelvin (deep blue clear sky).

Light Output: Since lamps (bulbs) are standardized, most fixtures will put out a given amount of light per lamp (e.g. 5000 lumens) times the number of lamps (e.g. 4) yielding a total of 20,000 lumens at the fixture. This doesn’t mean there will be 20,000 lumens at working height. The quality, design and cost of the fixture will determine how much light reaches the work surface.

You can have too much light as well as too little. If fixtures designed for high ceilings (e.g. >16 feet) are used for lower ceilings, the light can be painfully glaring. Similarly, the “color temperature” of the light can be less or more light natural light and therefore kinder to the eyes. A good lighting design will incorporate correct light output and color temperature with optimum positioning for the task(s) at hand.

Light output can be measured in lumens, lux or foot-candles. Using lumens as the unit, lamps are typically rated as follows:

• HID lamp: 40,000 lumens falling by 10% in 6 months and 30-40% in first 3-4 years
• T-12 lamp: 30-40% lumens drop over lifetime
• T-8 lamp: 10-12% lumens drop over lifetime if at correct temperature
• T-5 lamp: 10-12% lumens drop over lifetime if at correct temperate

Output and longevity of different fixtures and bulbs depends on the temperature of the ceiling where they operate. Too high or low a temperature can drastically shorten bulb life. This is even a problem with modern T-8 or T-5 lamps. Look for lamps with:

• Constant output ballasts which put out the same amount of light regardless of temperature (within certain limits)
• A manufacturers warranty on the lamp/ballast system

Replacing lamps (bulbs) can be a huge problem with high ceilings, so lamp longevity is crucial. The labor cost to replace a lamp is typically higher than the lamp cost. Some companies swap lamps on all fixtures in an area simultaneously whether they’re burned out or not, on the assumption that the ones that are not will probably burn out soon anyway. This is called group re-lamping and can save significant labor costs.

Replacing Fixtures during a retro-fit can be very expensive in terms of labor and material costs. If the optimum positioning and spacing between the new fixtures does not match the positioning of the old fixtures, new hanging points must be installed, with associated wiring. A good lighting designer will think through these issues in detail.

Payback can vary from 18 months to several years, depending on a lot of factors. Good lighting has to take into account various factors including:

• Ceiling height which reduces light delivered to the work surface
• Enough lumens for the task(s) at hand, which depends on output and positioning
• Initial lumens which will decline over the fixture life. (40% for magnetic ballasts, 10-15% for electronic ballasts.)
• Light quality, including color index
• Dimming in response to daylight and occupancy levels

Ballasts: Most of the energy savings over the last few years have come from improvements in ballast design. These include

• Constant output – the ability to put out the same amount of light regardless of temperature fluctuations
• Dimmability – the ability to reduce light output (and energy consumption) in response to daylight and occupancy sensing

Resources:

- Understanding Power Bills (PDF)

- See our List of Projects

- See An Online Auction Demo (you must register to view this demo)