When attempting energy savings, lighting is probably the first place in a facility to look for savings because changes are usually easy, inexpensive and have a quick payback period. The first step is to assess current lighting conditions. Measuring current conditions against calculated upgrades will present the expected savings. Understanding current lighting conditions and needs will aid in determining applicable opportunities and recommendations.
Assess Existing Conditions
To conduct a lighting audit we will first need to gather basic lighting information, such as the number of lights, their location, and their time in use to help you understand the current energy use attributed to lighting in the facility. This information will help you understand how much you are currently spending and the potential savings available from lighting efficiencies.
Methodology & Details
We prepare a fixture cost work sheet for each type of fixture found in a facility to establish the individual fixture costs found on the summary page of the payback work sheet. The fixture cost worksheets include the costs to run the LED which is recommended to replace the existing lamps.
Individual Fixture Costs
These Fixture Work Sheets are a part of the complete Payback Presentation & Establish for the Facility the overall costs per each Fixture. The total cost of a lighting fixture is made up of 3 integral parts.
1) Lighting Cost Per Year – The actual Lighting watts that an existing fixture draws which is mathematically converted to Kilowatt Hours (KWH) which is how your utility company charges you. Once the KWH amount is established it is multiplied by the average of a customer’s bills. Generally we try to have a winter bill, a summer bill and a fall bill, this way we take into consideration for averaging the higher kilowatt hour charges in the summer when utilities charge for extra A/C burden on the system. We then establish the customer’s usage period of the fixture and convert it to annual hours.
For example 24 hours a day, 7 days a week = 8760 annual hours of usage. This is purely a mathematical equation and utilizes actual customer numbers.
2) Cooling Costs Per Year – The Cooling Cost is the actual heat that a light fixture generates that has to be cooled by your HVAC system. Most people know if you touch a light bulb that it is very hot and will burn your fingers this heat is generated into a facility and has to be cooled. Each type of lamp generates certain BTU’s (British Thermal Units) per watt of the lamp and per hour. A Fluorescent fixture as an example generates 4.1 BTUs per watt per hour. This information and the formulas used to convert BTU’s to equivalent watts that your A/C system will use to cool the fixture is based on ASHRAE standards. Once the BTU’s are converted to Kilowatts it is then converted to KWH and multiplied by the customers established per kilowatt-hour price. Each area of the country cools for different periods. We use the established A/C weeks guideline developed by the US Department of Navy – Naval Civil Engineering. The customers hours of operation is then multiplied by the Navy’s listed weeks of A/C for the area.
Some facilities may in fact have reasons to cool beyond the standards however it is a general rule of thumb that we utilize the established weeks by the Navy. For example the facility runs 24 hours a day, 7 days a week but only cools 23.7 weeks of the year so the cooling costs are calculated as 24 X 7 X 23.7 = 3981.6 rounded to 3982 hours . This is the amount of hours used to determine cooling costs. This is purely a mathematical equation and utilizes actual customer numbers.
3) Maintenance Costs Per Year – The Maintenance Cost of the fixture is a true cost that all facilities encounter. In establishing maintenance cost we use the existing manufacturers specification of the time the lamp will run, the rated time of any ballasts and the number of times a maintenance person or electrician will have to service the fixture. The labour rate used is established by the US Department of Labor’s stated average wage rate for a electrical maintenance worker which is $55.00 per hour fully loaded with benefits. It should be noted that in an area that is governed by unionized electricians the rate would be much higher and conversely some building owners with their own maintenance staff may have a lesser rate. Our LED’s have a life span of 50,000 hours before replacement therefore the maintenance costs of the fixture is based on it being maintained over 50,000 hours. Once the total maintenance cost are established they are then divided by the number of years that the LEDs will last the customer based on the hours run to establish a per year maintenance cost.
Current Fixture Cost Factor Comparison
Once these fixture worksheet cost calculations are established for each of the fixtures in the facility a Current Lighting Fixture Cost Factor Comparison Chart is generated. This compares the existing with the LEDs that will retrofit the fixture. The first section is the cost factors of each existing fixture along with the corresponding cost factors of converting the fixture to LED’s. From these cost factors savings are determined, payback per fixture is calculated and overall 50,000 hour savings are generated along with net savings after the purchase of the LED product.
Savings & Payback Calculations
The individual fixture costs from the Fixture Cost Factor Comparison Table are then multiplied by the number of the fixtures in the area and presented in the Savings & Payback Calculation Table of the payback presentation to show the over all facility savings and paybacks. Current Costs, New LED Costs, Annual Savings, Purchase of LEDs and 50,000 hours savings are then all totaled. The Total Purchase of LEDs for the facility is then divided by the Annual Savings which is multiplied by 12 to determine the payback to the customer in months. The payback is converted to annual dollar savings and the Cumulative totals indicate the dollars saved year by year. The Return on investment is based on the 50,000 hours savings total divided by the cost to retrofit to LED equaling the percentage of return.
The annual lighting KWH and the annual cooling KWH are added together to determine the Carbon Foot Print expressed in pounds of Carbon Dioxide. One KWH = 1.341 pounds of CO 2 based on DOE EPA Statistics. The LED Energy Systems Payback Presentation is intended to be conservative. It does not factor in any increase in utility rates, any obsolescence of ballasts, any shortage of existing lamps due to changing government regulations ie) banning of incandescent in 2012, nor does it factor in any rebates at the utility level, State level or Federal level.