Studies Show: HVAC System Maintenance Saves Energy
By Institute for Building Efficiency
Fewer than half of companies perform preventive or predictive maintenance on their building HVAC systems – even though studies show that good maintenance can cut HVAC energy costs while also extending equipment life, improving occupant comfort, and increasing uptime. Effective maintenance can reduce HVAC energy costs by 5 to 40 percent depending on the system or equipment involved. A variety of HVAC components need ongoing maintenance or energy performance degradation can occur.
HVAC System Maintenance
Regular scheduled maintenance of heating, ventilation and air conditioning (HVAC) systems can increase their efficiency, and a number of studies have quantified energy savings from maintenance, as well. These studies fall in two categories:
1. Analysis of failures in individual HVAC components and the energy savings possible by correcting those failures.
2. Whole-system estimates based on interviews with HVAC maintenance experts. Energy Performance and HVAC Component Maintenance
HVAC systems have over 100 components, and many common component performance issues degrade energy performance. The following chart summarizes studies of the potential energy savings from good maintenance on chiller components with the greatest energy impacts.
Estimating Whole-Building-System Energy Savings from Maintenance
A few studies have analyzed the whole-building energy savings from HVAC system maintenance.
• The New Buildings Institute found that best practices in building maintenance and operations reduce energy use 10 to 20 percent across all climate zones in the United States. In contrast, poor maintenance practices can increase energy use by 30 to 60 percent.11 The study included HVAC systems setpoints and schedules, economizer operation, ventilation controls and settings, and HVAC system efficiency and fan power (these last two variables were included as surrogates for adequate maintenance and balancing of the HVAC system).
• Portland Energy Conservation Inc. found that building operation and maintenance programs specifically designed to enhance the operating efficiency of HVAC and lighting systems decreased energy bills 5 to 20 percent in commercial buildings, without significant capital investment.12
• The National Center for Energy Management and Building Technologies conducted 45 interviews with industry experts, and concluded that effective scheduled maintenance decreases energy bills 15 to 20 percent in commercial buildings.13
Management Approaches to Capture HVAC Maintenance Savings
Often, energy savings opportunities through maintenance are missed. There are three basic approaches to maintaining HVAC systems in buildings:
1. Reactive maintenance. Under this management practice, used by 55 percent of companies, HVAC systems run until a problem or failure occurs.14 (This strategy also called run-to-fail maintenance.)
2. Preventive (or scheduled) maintenance. This practice, used by 31 percent of companies, the periodic maintenance of HVAC equipment, generally as prescribed by the manufacturers.15
3. Predictive maintenance. Practiced by 12 percent of companies, this strategy differs from preventive maintenance by basing maintenance on the actual condition of the machine, rather than on a preset schedule. Predictive maintenance can be the most cost-effective over the long term, but does require technology infrastructure investments up front.
Regularly scheduled maintenance of HVAC systems can increase the energy efficiency. While the initial data is encouraging, more quantification of the energy savings will lead more building owners to become interested in regular maintenance for their HVAC systems. More studies are needed to accurately quantify the energy savings from varying maintenance strategies, as well as the return on investment from maintenance activities. The HVAC industry can develop better tools to help building owners and facility managers evaluate the relationship between maintenance costs and energy costs and support investment in the appropriate maintenance approach.
Related Article: Can More “Usable” Thermostats Save More Energy in Small Buildings?
1 Maximizing Chiller Efficiency. Maintenance Technology Magazine. [http://www.efftec.com/resources/maximizing-chiller-efficiency.php]
2 Iowa State University’s Center for Industrial Research and Service. Energy-Related Best Practices: A Sourcebook for the Chemical Industry. Chapter 6. [http://www.ciras.iastate.edu/publications/EnergyBPChemicalIndustry/]
3 MEASURE 2.7.2 Maintain the proper refrigerant charge. [http://www.energybooks.com/pdf/342346.pdf]
4 ASHRA E. “Effects of Oil on Boiling of Replacement Refrigerants FlowingNormal to a Tube Bundle.Part 1: R-123 and Part 2:R-134a”
5 Kevin Graham. 5 Steps to Chiller Efficiency. 2004. [http://www.facilitiesnet.com/hvac/article/5-Stepsto-Chiller-Efficiency–2192] 6 Kevin Graham. 5 Stepsto Chiller Efficiency. 2004. [http://www.facilitiesnet.com/hvac/article/5-Stepsto-Chiller-Efficienc–2192] 7 Maximizing Chiller Efficiency. Maintenance Technology Magazine. [http://www.efftec.com/resources/maximizingchiller-efficiency.php] 8 Iowa State University’s Center for Industrial Research and Service. Energy-Related Best Practices: A Sourcebook for the Chemical Industry. Chapter 6. [http://www.ciras.iastate.edu/publications/EnergyBP-ChemicalIndustry/EnergyBestPractices-ChemicalIndustry-Sourcebook.pdf] 9 Alan Cowan. Review of Recent Rooftop Unit Field Studies in the Pacific Northwest and California. New Buildings Institute. 2004.
10 Alan Cowan. Review of Recent Rooftop Unit Field Studies in the Pacific Northwest and California. New Buildings Institute. 2004.
11 Frankel, M., Heater, M. and Heller, J. “Sensitivity Analysis: Relative Impact of Design, Commissioning Maintenance and Operational Variables on the Energy Performance of Office Buildings” New Buildings Institute. August 2012.
12 Portland Energy Conservation 1999c. Operation and Maintenance Assessments: A Best Practice for Energy-Efficient Building Operations. September 1999.
13 Chimack, M. J. Aardsma., D. Novosel. Energy Reduction through Practical Scheduled Maintenance. National Center for Energy Management and Building Technologies. November 2006.
14 Sullivan, G.P., R. Pugh, A.P Melendez, and W.D. Hunt. Operations and Maintenance Best Practices: A Guide to Achieving Operational Efficiency Release 2.0 U.S. Department of Energy. July 2004.