H-MOSS® Return on Investment
Explanation of Calculations
# UNITS
Total number of fixtures in area.
WATTS PER UNITS
Total number watts per fixture including ballast.
TOTAL WATTS
Equal to # UNITS times WATTS PER UNIT.
KILOWATTS
Lighting loads are rated in watts; however, a utility company’s bill is shown in kilowatt-hours. Therefore, we must divide the TOTAL WATTS by 1000 to determine the KILOWATTS.
RATE/kWh
All utility companies charge for electricity in terms of dollars per kilowatt-hour. The Bureau of Labor Statistics reported that the national average for commercial users is $.0736/kWh. They calculate this number by adding up all of the kilowatt-hours consumed divided by the gross sales billed excluding “sales tax”. This accounts for all surcharges, demand billings, taxes (other than sales tax), time of day or year billings, etc. This gives a true cost of energy. To determine your true cost of energy, or rate, simply use a current monthly utility bill and read off two numbers: (1) kWh Consumption, and (2) Total Cost.
Rate = Total Cost/kWh Consumption
ANNUAL OPERATING HOURS
Estimate the average hours per day the area is lit. Even though the area is occupied 8 to 9 hours per day, the lights are usually on 12 to 14 hours per day. Also, many times the lights are on weekends and holidays. Multiply the hours per day times the number of days per week times 52 weeks per year. For example: 12 HOURS/DAY X 5 DAYS/WEEK X 52 WEEKS/YEAR = 3120 HOURS/YEAR.
PERCENT SAVINGS In almost all cases a savings of 30 - 60% will be achieved. If employees work odd hours, weekends, holidays, or double shifts, savings may exceed 70%. If a sound energy management system is installed with sophisticated lighting control strategies, the savings may drop to 25 - 30%; however, most systems don’t do a good job with lighting control. The only way of determining actual savings is to meter the area as is, then install the H-MOSS Sensors and meter again. Typical reasons for waste are:
- Lights on before and after work schedule.
- Lunch time and coffee breaks.
- Periodic meetings throughout the day.
- Lights are on until cleaning staff completes cleaning facility.
- Lights left on all nights or over weekends and holidays.
PAYBACK CALCULATION
Payback is the time in months that the H-MOSS system will pay for itself in energy savings. This can be as few as several months. Typically, a two year or less payback is considered adequate to justify an investment in occupancy sensors. To determine payback, take the cost of the material used for the installation, divide by the annual dollar savings then multiply by 12. For example: MATERIAL COST = $100.00, SAVINGS = $50.00; $100 (material costs) / $50.00 (savings) x 12 = 24 month payback period.
EXAMPLE
A typical office might have:
LAMPS: 4 - 2’ x 4’ fixtures (4 x 0.184) = 0.736 kW
RATE: $0.0784 / kWh
OPERATING HOURS: 12 hrs/day, 5 days/week or 3120 hrs/yr.
PERCENT SAVINGS: 50%
ESTIMATED ANNUAL SAVINGS: (0.736) x (0.0784) X (3120) x (50%) = $90.02
MATERIAL COSTS: $95.00 PAYBACK: ($95.00/90.02) x 12 = 12.8 months
This calculation is provided for you on the ROI work sheet shown below. Click the image for a larger view, or download the excel sheet. [Right Click, Save Target As...]
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