Lighting Research Center Lighting Research Center

Residential Lighting

Explanation of Results from Economic Worksheet
Design 1 The existing design, the common practice used by a builder, or any other point of reference.
Design 2 The new or alternative design.
A
Lamp/Ballast watts
Enter the input power of one lamp including the ballast. See the manufacturer's information on the package or refer to the manufacturer's catalog. Some lamps have different lamp and ballast combinations. Input power will vary with ballast manufacturer, type of ballast and the number of lamps that are operated per ballast.
B
Number of lamps
Tally the total number of this type of lamp in your Design 1 and Design 2.
C
Power Reduction Factor
If the lamps usually are operated at full power, enter 1.

If multiple-level switching is used, estimate the average power reduction. For example, if only half of the lamps are operated most of the time, enter 0.5. If a 50-100-150 three-way incandescent lamp is operated at equal amounts on all three settings, enter 0.67 (100 watts average divided by 150).

If dimmers are used, see Table 1 for the appropriate power reduction factor. Often dimmers are used for occasional variation of illuminance, not for regular reduction of power. If so, enter 1. Using lower-wattage lamps is usually a better economic choice than using higher-wattage lamps that are dimmed all the time.

D
Lamp's Daily Operation
Estimate the average hours of one lamp's operation per day. Consider the impact of timer controls such as occupancy or photosensors on your estimate. For example, if a security light that operates 24 hours per day is controlled by a photosensor, enter 12 hours for the average hours of lamp operation.
E
Motion Detector Factor
Enter 1 if no motion detector is used. If a motion detector is used, estimate the fraction of the daily hours of lamp operation in D when the room is occupied or the lamps must be operated. For example, if the lamps in a bathroom usually are operated 4 hours per day, but the bathroom is unoccupied for one of these hours, and a motion detector is to be installed, enter 0.75. See Table 2 for more information.
F
Cost of electricity
Enter the average cost of electricity for the location being considered in the analysis. Electricity costs in North America range from $0.03 to $0.18 per kWh. For this site, $0.10 per kWh is used for examples. Check with your local utility to verify your rate. Some utilities have seasonal rates that can be averaged to calculate an annual rate.
G
Average rated lamp life
Enter the average rated lamp life from the manufacturer's catalog.
H
Lamp life multiplier
For incandescent lamps, enter 1 because incandescent lamps are not greatly affected by hours of operation per start. If a dimmer is used, however, see Table 1 for a lamp life multiplier for incandescent lamps.

For fluorescent lamps, enter the lamp life multiplier from Table 3.

I
Price of one lamp
Enter the price of one lamp used in each design.
J
Amount of incentive
Enter the total amount of an incentive, if any is available. If there are no incentive, enter zero. Some electric utilities offer discounts, rebates, promotions, and other incentives to reduce the cost of energy-efficient equipment. For example, if two compact fluorescent lamps are being considered and each has a $5 rebate, J is $10.
K
Price of lamps
Enter the total price of the lamps used in each design (B x I). If Design 1 and Design 2 both use the same number and type of lamps, enter zero for both.
L
Price of ballasts
Enter the total price of the ballasts used in each design. If Design 1 and Design 2 both use the same number and type of ballasts, enter zero for both. Prices vary, so check with your ballast supplier for an accurate price estimate.
M
Price of luminaires
Enter the total price of the luminaires used in each design. If Design 1 and Design 2 both use the same number and type of luminaires, enter zero for both. Prices vary, so check with your luminaire supplier for an accurate price estimate.
N
Price of controls
Enter the total price of the controls used in each design. If Design 1 and Design 2 both use the same number and type of controls, enter zero for both. Prices vary, so check with your control supplier for an accurate price estimate.
O
Cost of labor
Enter the total cost of labor to install each design. Consider the labor costs of the electrical work and any carpentry or repair work that is not included in both cases. Verify costs with your electrician and/or carpenter.



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