Introduction
As a basis for evaluating and comparing the costs and benefits of alternative lighting system designs, a Life Cycle Cost (LCC) Comparison Template has been developed. The LCC Comparison Template accounts for all costs, including construction costs, energy costs, re-lamping costs, cleaning costs, and repair costs, through the life of a lighting system. It is a metric for comparing economic and energy effects, but not of lighting quality or efficacy.
ENERGY EFFICIENCY
The principal measure of an energy efficiency design is the electrical lighting system’s connected lighting power density (LPD), measured in watts per square foot (W/sf) and the energy-saving effects of its electric lighting controls. Energy equals power multiplied by time. Lighting controls that reduce power (by dimming) and time (by switching some or all lamps off) must be included in the evaluation of energy efficiency.
The design’s LPD should be 0.90 W/sf or less for all lighting intended to be operating simultaneously. Typically, general light levels can be achieved at around 0.78-0.85 W/sf.
template
A LCC Comparison Template is based on a standard classroom model and three sample lighting systems—you will need to make adjustments to account for the unique qualities of your own classroom designs.
LCCs are often expressed as “present value,” a means by which future costs are discounted, allowing a total cost to be determined by which competing systems can be compared. The Life Cycle Cost (present value) of a classroom lighting system using this spreadsheet should not exceed $6.50 per square foot. The costs of various lamp and ballast combinations may be tested in the LCC Comparison Template.
To account for energy savings due to daylighting, two numbers must be considered: 1) a reduction factor for lighting energy for any classroom with automatic daylighting controls (see table below); 2) minimum average daylight level of at least 10 footcandles. A higher savings value may ONLY be used when computer calculations result in higher minimum average light levels on March 21 at noon in Southern California, according to the following table:
Energy Reduction due to Daylight – Factor Table
Lowest average daylight level 9AM-3PM any time / Reduction percentage using single zone switching / Reduction percentage using multi-zone switching / Reduction percentage using dimming10 fc / 5percent / 10percent / 20percent
20 fc / 10percent / 20percent / 30percent
25 fc / 20percent / 30percent / 40percent
30 fc / 30percent / 40percent / 50percent
35 fc / 40percent / 50percent / 60percent
40 fc / 50percent / 60percent / 70percent
SCE Classroom Lighting Guide 3 September 2004 SCE+Lighting+Guide.htm
SCE Classroom Lighting Guide 3 September 2004 SCE+Lighting+Guide.htm