Chattanooga, TN: Energy performance

Better Buildings Challenge Partners strive to decrease portfolio-wide source energy use intensity (EUI) and to increase the percent improvement compared to a set baseline. The City of Chattanooga's portfolio consists of more than 120 buildings and 1.7 million square feet. The City of Chattanooga has improved energy performance by 36% from a 2013 baseline. *Energy consumption during 2020 was significantly lower than a typical year since COVID-19 disruptions resulted in temporary building closures and reduced occupancy for much of the year.

However, due to ongoing occupancy by critical core staff throughout the majority of the year, most municipally owned facilities included in the Challenge continued to operate on normal schedules and temperature set points and setbacks established with building automation systems. These systems are in place and operating in over 30 of the City's primary facilities. Additionally, ongoing improvements and upgrades, such as boiler replacements and completion of a 60+ facility LED lighting retrofit project, contributed to the reduction in energy consumption and improvement to EUI. Following a nearly full return to in-office work policy for the City in 2021, only a modest 4% increase of EUI was recorded.

The EUI improvements were largely maintained through a portfolio of energy savings projects which will have lasting impacts for City operations. These include the City's first Showcase Project, the downtown Public Library, which has completed the replacement of over 800 fluorescent bulbs with just over 100 LED lights, as well as replacement of a 40-year HVAC system. Through these efforts, the library has realized a 41% reduction in energy consumption and has provided over $60K in annual savings. Construction of an electric microgrid serving the City's public safety campus began in spring of 2021 in partnership with the municipal electric utility (EPB), and has just undergone final testing and completion. The campus houses the police and fire departments, as well as radio communications services used by emergency responders. The microgrid will increase the campus' energy security and operational resilience in the face of increasing risk of man-made and natural disasters while further reducing EUI and increasing the amount of power supply to the City from non-carbon based sources. *Based on data provided by the utility, the microgrid is providing the campus an average annual usage savings of 25% and over $17K in annual electricity costs. [*Solar generation at the campus began in November of 2021 and data reflect total savings through October 2022.] Lastly, the City's Moccasin Bend Environmental Campus, which serves as a regional wastewater treatment facility for a 6-county area, has installed a 4-megawatt solar array which now provides approximately 10% of the Campus' 'behind-the-meter' power and over $400K in annual electric utility savings. This project, in addition to several other energy-related projects, has resulted in a total savings of 27% at the campus, which accounts for over half of the municipal government's energy demand.

Looking at the percent improvement in energy performance across all buildings can provide insight into how an organization is saving energy.  The City of Chattanooga has achieved energy performance improvement of greater than 15% at more than 50 of its buildings with several of the city's properties experiencing even greater energy performance improvements. Although at this early stage there are 6 buildings that have experienced an increase in Source EUI, armed with the key performance metrics provided through utility monitoring in Portfolio Manager, the city is able to shift its focus on strategic improvements to the lowest performing properties that will result in the greatest energy performance payback for the capital invested.

Property-level energy performance metrics, including EUI and percent improvement to date, are critical to track progress over time and identify opportunities for additional energy savings. Chattanooga's building portfolio consists of a wide range of property-types which results in a portfolio with a wide range of baseline EUI values. While the majority of the city of Chattanooga buildings have shown energy improvement since the baseline of 2013, the properties located near or below the 0% axis may indicate properties that present good opportunities for further improvement in energy performance and savings.