Back in October, we told you about ASHRAE’s co-sponsored Advanced Rooftop Unit (RTU) Campaign, which encouraged commercial building owners and managers to replace packaged RTUs with energy-efficient systems or retrofit them with advanced controls. A year-long field study conducted by the Department of Energy’s Pacific Northwest National Laboratory (PNNL) proved commercial buildings could cut their electricity use by an average of 57 percent with advanced energy efficiency controls.
The PNNL team retrofitted a total of 66 RTUs at eight commercial buildings in Washington state, Ohio, California and Pennsylvania with advanced controls. One-minute interval data was collected from the units over a 12-month period. They compared the results to the buildings’ energy consumption pre-retrofit (without advanced controls) and found that:
- Advanced RTUs resulted in an average of $1,489 energy savings per year.
- Advanced RTUs reduced energy consumption by 22 to 90 percent, depending on the size of the unit.
- Energy savings increased with size of unit.
- Large units (e.g., greater than 15 tons) and units with long runtime (e.g., 24/7 operations) had the shortest payback periods.
- Upfront costs of installing or retrofitting systems with advanced controls could be recovered in an average of three years.
Based on the results, PNNL concludes that approximately 285 trillion Btus of energy could be saved if just 50 percent of the packaged RTUs in the U.S. were retrofitted with advanced controls. That’s equivalent to removing more than 70 coal-powered power plants or more than 10 nuclear power plants.
Click here for the complete field study results. For a summary of the findings, read the “Improving Operating Efficiency of Packaged Air Conditioners & Heat Pumps” article in the March 2014 issue of ASHRAE Journal.