Calculating Your HVAC Energy Savings In An LED Retrofit
November 10, 2020
This is the second article in our latest series: Calculating Your Savings and ROI on any Lighting Project. Please also see: Calculating your Lighting Only Energy Savings, Calculating your Maintenance Savings Part 1 & Part 2, Calculating your ROI.
For some of the calculations in this article, you will need to have completed the calculations from: Calculating Your Lighting Only Energy Savings.
Your return on investment savings (ROI) from a LED retrofit project can come from surprising places, including HVAC savings. It is one of the least commonly covered subjects when your calculating energy savings. Lamps do emit heat that naturally rises, so switching to energy-efficient LED lamps can impact your heating and air-conditioning costs.
If you use air-conditioning in the workplace, calculating HVAC energy savings will give you a better idea of how the lighting retrofit project will impact your company’s bottom line.
Step-by-Step Calculations for HVAC Energy Savings from LED Lighting
Your old lighting system emitted a ton of heat. Since heat rises, employees might not have noticed it but your monthly air-conditioning costs would have reflected the added heat especially in the summer months.
The newly installed LED lights that replaced your old lamps do emit much less heat, but to find your HVAC savings from the lighting project you’ll need to perform a few simple calculations.
Step 1: Collect the Necessary Information
You’ll need to get the following information to determine your lighting and HVAC savings.
- The total yearly energy savings per lamp. For this example, we’ll use 328 kWh saved annually per LED lamp, since this was the figure we used in Calculating Your Lighting Only Energy Savings. If you missed that article, you can click here to find those savings calculations.
- Estimated time the air conditioner is running annually. A study conducted by the S. Department of the Navy, Naval Civil Engineering Lab, CR82.028 in 1982 found on average air conditioners in Madison, Wisconsin operated 38.85% of the year or 4.6 months. The data does not apply to warmer regions or take into account global warming which has increased air conditioner use in the years since the study was published. For this sample equation, will use the Naval study usage rate of 38.85%.
- The electricity rate. Electricity rates vary depending on provider and location. The average rate is $0.12/kwh which is what we’ll use to determine the lighting and HVAC savings.
Step 2: Calculate the Percentage of the Year Your A.C. is Running
You only want to calculate your LED lighting and HVAC savings for the months the air conditioner is running. Following the Naval study data, here is the equation to find the percentage:
Months of Cooling ÷ 12 months = the percentage of the year when the air conditioner is working. If you use the company’s A.C. for 4.6 months annually your calculations are
4.6 months of cooling ÷ 12 months in a year = 38.33% of the year the air conditioner is operating.
Step 3: Calculate Energy Savings from Reduced HVAC Operating Time
You already know how much you are saving annually per lamp, 328 kWh. You also know the annual percentage time the air conditioning unit is running, 38.33%. When you’re calculating your HVAC energy savings, you also need to determine the number for the ASHRAE rule. The rule refers to a federal commission that monitors energy conservation numbers in organizations.
The ASHRAE rule for this equation is .33 percent. So to calculate your energy savings from reducing HVAC operating time you’ll multiple the yearly savings by yearly percentage A.C. is on, by the ASHRAE rule.
328 kwh x 38.33% A.C. operational time x .33 ASHRAE Rule = 41.49 kWh of HVAC savings annually.
Step 4: Calculate Dollar Savings From Reduced HVAC Use
You know that you are reducing electrical costs, but how much are you saving on your LED lighting retrofit project annually? Calculating your energy savings per lamp starts with a simple equation.
You are savings 41.49 kWh annually in HVAC electrical usage, multiplied by your electricity rate of $0.12/kwh. The resulting answer will tell you how much each energy-efficient LED lamp is saving the business annually.
41.49 kWh saved x $0.12/kWh = $4.97 saved per lamp annually. The savings per lamp may not look like much until you multiply it by the number of lights that were installed.
Know Your HVAC Energy Savings
That wasn’t so hard was it? We understand that a lot of organizations don’t factor in the HVAC savings for an LED retrofits, but it is important for estimating paybacks and knowing the full impact of your lighting project. To speak with an Action Services Group LED lighting specialist, call us today at 610-558-9773, email [email protected] or schedule a call.
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