There are many documented procedures that will reduce energy consumption and cut utility costs—facilitating them is the fun part, when sleeves are rolled up and hands are dirtied, installing, balancing, calibrating, and programming high-tech equipment purchased by a facility to make dreams of energy savings a reality.
However, getting to this point is contingent upon first achieving buy-in from decision-makers who must finance the efficiency program. Sometimes—perhaps more often than not—that buy-in isn’t achieved, and the program never takes shape.
According to The Association of Energy Engineers’ Economic Analysis Handbook, when it comes to securing a financial commitment from key decision-makers, the first step is to provide a complete and detailed economic analysis. This involves formulating, estimating, and evaluating the economic outcomes of the various procedures available to accomplish a specific end or goal.
The decision to select one (or more) of these choices will be made based on data, analysis, and comparison of the costs and benefits of each choice. Decision-makers need an economic analysis when deciding if a project is cost-effective, and whether it will subsequently be implemented. One of the first steps to take when creating this analysis is establishing a building’s energy usage.
An Energy Usage Index (EUI) is defined as the total amount of energy used by a building (electricity and natural gas) per square foot of floor area (annually), and it is used to establish a facility’s baseline energy use. Knowing how much energy is used is critical to determining possible savings—simply identify all the energy used in a facility and add up the Btu.
Next, find the total square footage of conditioned space and divide the total Btu used per year by the square feet of space. A building’s EUI value can be used in a similar manner as miles per gallon is used to describe the efficiency of an automobile. It allows you to compare your facility’s total yearly energy use to industry standards or your peers. It can be a great first step in determining if your facility is on—or off—the energy mark when compared to others.
For example, a facility with 10,000 square feet of conditioned space uses 100 MMBtu of gas and 150,000 kilowatt-hours (kwh) of electrical energy in one year. What is the building EUI?
- Btu (gas) = 100 MMBtu = 100 X 106 Btu/year
- Btu (electrical) = 150 kwh X 3,412 Btu = 511.8 X 106 Btu/year
- EUI = (100 + 511.8) x (106)/ (10,000 ft2) = 61,180 Btu/square foot/year
The EUI establishes a facility’s overall energy use that can be used to formulate an energy-savings strategy. Some typical healthcare facility EUIs are shown by region of the United States in Figure 1.
Figure 1. The U.S. Commercial Buildings Energy Consumption Survey, U.S. Energy Information Administration, shows primary energy usage by census region and principal building activity intensity (thousand Btu per square foot per year).
After calculating a building’s EUI, next determine specifically where the energy is being consumed and target those areas that show the greatest use. Unless energy meters are already installed on each piece of equipment, this determination will be made using an industry average. Be sure to take local influences into account, as it will help your energy analysis by reflecting a more accurate estimate of the real savings potential.
Figures 2 and 3 reflect the result of typical hospital usage profiles found in the ASHRAE HVAC Design Manual for Hospitals and Clinics, in which Houston serves as the baseline for the South Central region’s energy consumption data.
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