Cities, communities and campuses throughout the nation are actively seeking more resilient, sustainable energy infrastructure to support economic growth and achieve environmental objectives. District energy microgrids incorporate combined heat and power (CHP) to deliver greater energy efficiency and optimize the use of local resources while strengthening the local and regional power grids.

The International District Energy Association (IDEA), the Microgrid Resources Coalition (MRC), and the Environmental and Energy Study Institute (EESI) held a briefing providing policy guidance and showcasing proven technologies and exemplary cases that illuminate the potential for more robust U.S. investment in district energy microgrids.


Rob Thornton, President & CEO, International District Energy Association

  • U.S. power plants, on their best days, are only about 32 percent efficient. One third of their output is usable energy (in the form of electricity) while the other two-thirds is lost as heat. This means there is an incredible opportunity for growth of district energy by capturing the waste heat and greatly improving the efficiency of the system.
  • In fact, the waste heat from U.S. power plants is greater than the total energy used in 197 different countries around the world.
  • Cities are not only embracing renewable energy, they are also becoming more open towards local power plants. When a power plant is located near its end users, it opens the door for opportunities to use the heat emitted when power is generated.
  • The beauty of the district energy system is that it essentially establishes an underground thermal network that connects multiple buildings and allows them to incorporate energy technologies that would normally not be feasible on an individual scale.
    • For example, 99 percent of the buildings in Copenhagen, Denmark, don’t have boilers. They get heat from a district heating network.
    • The city of Toronto actually uses a thermal network to cool the city.
  • By combining cooling, heating, and electrical power, we can dramatically improve the efficiency of our energy systems in the United States. Thermal networks allow cities to improve energy efficiencies from 30/40 percent to 70/80 percent.
  • We are now seeing natural drivers that demonstrate the need for resilient electricity systems like microgrids. Extreme weather events, droughts, and wildfires pose challenges to the electricity industry. These events expose the fact that a lot of America's energy infrastructure is out-of-date and in need of renewal.
  • Superstorm Sandy was a huge galvanizing moment for the Northeast.
    • Over 8 million homes lost power, causing more than $70 billion in lost business.
    • Some district energy systems were able to stand up to Sandy.
      • For example, the 40 MW co-gen plant in Co-Op City in the Bronx not only maintained power, it also helped Con-Ed (the local utility) restart its grid.
      • Princeton University’s energy system also stayed on through Sandy (and Hurricane Irene), allowing it to save its critical research and be a hub for the community.
  • It’s hard to ensure a city will keep its power on if its power plant is 100 miles away. Cities want local power plants similar to what Princeton University has, which leads to:
    • Greater efficiency.
    • Greater resiliency.
    • Systems that can integrate with intermittent renewables like wind and solar.
    • The ability to tap into local energy supplies, which can boost local economies.
    • A reduction in greenhouse gas emissions.
  • Mayors and governors in the states affected by Superstorm Sandy have realized that they cannot proceed as usual. This has led to state policies that support technologies like district energy.
  • Many states will proceed with making their power generation cleaner and more resilient, with or without the Clean Power Plan. In fact, over 290 district energy systems in the United States have already done the hard work (installing a thermal network) and just need to add cogeneration to their systems.


Ted Borer, Energy Plant Manager, Princeton University

  • District energy is not a red issue or blue issue. Both sides are interested in energy savings and increasing energy efficiency.
  • Highly-integrated microgrid systems exist today, and Princeton is just one example of what you can do with a microgrid system. To give a sense of scale, Princeton University has 180 buildings, including dormitories, administration buildings, athletic facilities, and classrooms.
  • What can we do with microgrids?
    • In the event that the power grid fails, microgrid systems can operate autonomously, protecting users from losing access to power.
    • Communities without microgrids can benefit just by being in the proximity of a microgrid. For example, first responders in Superstorm Sandy were able to benefit from Princeton’s microgrid to recharge their electronic devices before returning to other surrounding communities—key for public safety communications.
  • Having a central power plant at Princeton makes it possible to centralize all the potential problems locally and allows for a simpler approach towards addressing issues. This costs more upfront but reduces cost throughout the lifecycle of the power plant.
  • Combined heat and power (CHP) is also known as cogeneration. Cogeneration efficiency hovers around 70 percent, but can sometimes reach up to 90 percent. Princeton’s gas turbine on its own is only around 34 percent efficient, but CHP dramatically improves that efficiency.
  • Princeton’s Economic Dispatch System is one thing that largely separates Princeton from much of the district energy crowd. The system allows the university to collect data to fully understand its energy needs. The data feeds into a 24-hour forward prediction model, which gives the university the ability to predict the community’s energy demand in advance, and forecast the cheapest times to buy (rather than generate) electricity.
  • Microgrids make the entire grid more resilient by making the network less vulnerable to outages and weak spots. They also reduce the need for spare capacity, which is often simply idle.


Michael Rooney, Manager of District Energy Initiatives, University of Pittsburgh Center for Energy

  • Why does district energy matter?
    1. It creates economic development and benefits for the people who live in the local community.
    2. It creates resilience at a community level.
    3. It gives communities the ability to build resilience by addressing infrastructure.
  • The City of Pittsburgh and the University of Pittsburgh recently began to look at opportunities for investment in energy and wanted to collaborate to become a leader in energy systems. This led to the District Energy Pittsburgh Initiative. The goals of this partnership were to:
    1. Modernize existing systems for the future.
    2. Identify new opportunities for microgrids, CHP, and district systems.
    3. Bring these groups together to deploy new technologies.
    4. Focus on workforce, resiliency, reliability, security, and economics.
  • The grid of microgrids concept was developed by Pittsburgh. Microgrid districts throughout the city support buildings like hospitals and 911 call centers.
    • The goal is to create interconnections between the systems to promote business continuity.
    • There is also a socially-responsible component to the concept. The city wants to ensure it is positioned to support not only businesses, but also citizens in the event of extreme weather.
  • Why does energy infrastructure investment matter to Pittsburgh?
    • Resilience or the ability to bounce back from social, environmental, and economic stresses.
    • Reliability
    • Sustainability
    • Security
    • Economics
    • Workforce development
    • Opportunity


Jim Lodge, Vice President of NRG energy

  • Resilience, reliability, and sustainability are keys to making microgrids happen.
  • District energy systems can be feasible even in regulated states.
    • Arizona State University (ASU) is a sustainability-postured campus located in a regulated state. The campus boasts 16 MW of on-site solar, 6 MW of thermal storage, 8 MW of diesel generation, and is also powered by NRG’s Sun Devil Energy Center CHP System.
    • The NRG CHP system is on site to help support the research laboratories in the event of a power failure [loss of power can be devastating to expensive research projects and scientific experiments].
  • The real challenge is integrating all the sources of energy and then optimizing the entire system so that supply balances demand.
    • If you can’t make the economics work, many of these projects won’t get off the ground.
    • Balancing intermittent energy technologies (like wind and solar) is not only the key, but also the challenge for systems to remain nimble.
  • The key components that will promote the growth of district energy, CHP, and microgrids are:
    • Recognizing and valuing the resiliency and reliability they provide.
    • Obtaining local support from stakeholders and champions.
    • Support from government and utilities.
    • Sustainability/efficiency drivers, the desire to integrate renewables and energy efficient technologies.
    • The right timing for deploying the technologies.
    • Economics/capital needed to make the project happen.
  • There’s plenty of opportunities to develop new projects, but also opportunities to turn old projects into microgrids.


District energy systems distribute thermal energy (steam, hot water, and/or chilled water) through a network of underground pipes to multiple buildings in an area, such as a downtown district, college or hospital campus. By aggregating the heating and air conditioning supply for multiple buildings, district energy systems optimize thermal energy efficiency. Moreover, they can use surplus heat from power plants, industrial processes and local renewable sources to cut emissions, reduce energy consumption and strengthen local economies. Combined heat and power (CHP) refers to facilities that simultaneously generate electricity and useful heat, thereby achieving very high efficiencies—more than 80 percent in many cases. Microgrids are robust electricity networks that can be operated in parallel with, or independently of, the utility grid. These three technologies complement each other and can be implemented together, optimizing the whole energy system and creating much greater resilience, which is especially important when extreme weather events occur.

Learn more with these brief informational videos: