In 2012, I visited the construction site of Deep Space, one of the largest underground auditoriums in the world. It was the latest project at the 1,100-acre “Intergalactic Headquarters” of Epic Systems, a medical software company in Verona, Wis., just outside Madison, Wis. The auditorium spans 1.2 million square feet and seats up to 11,400 people. With three massive LED screens—including one that stands 68 feet tall—the space generates significant heat during events.

To maintain comfortable temperatures in Deep Space and approximately 40 other campus buildings, Epic relies on an extensive underground geothermal heat exchange (GHX) system. This system conditions air temperature throughout the campus by circulating water through pipes and transferring heat beneath the earth’s surface. Onsite solar and wind installations power components of the GHX system and provide 20 percent of Epic’s electricity needs, resulting in substantial energy savings and a significantly reduced carbon footprint.

This column explores the technical details of this large-scale GHX system and profiles the company that took a significant financial risk to build it. It also examines the partnership between University of Wisconsin (UW)-Madison and Epic, which transformed the GHX system into an important laboratory and research platform. The collaboration serves dual purposes: monitoring and optimizing performance for Epic’s operations while generating critical data on the long-term viability of large-scale geothermal systems. Insights gained through monitoring and analysis will inform future projects and expand the field’s developing knowledge base.

Epic’s GHX System

While communities have used geothermal energy for decades, it has gained wider appeal in recent years due to reduced carbon emissions, energy efficiency and lower operational costs. GHX systems leverage the ground’s stable temperature—approximately 55 degrees Fahrenheit—to condition fluctuating above-ground air temperatures throughout the year. Rather than producing energy, these systems improve efficiency by reducing the workload on conventional heating and cooling equipment.

Epic’s system employs electric heat pumps and a closed-loop pipe network to circulate water underground through vertical boreholes. The water carries heat from buildings—including the auditorium and data center—into the ground during summer, returning cooled air. In winter, the process reverses, recovering stored heat from the earth. These systems use the ground like a “thermal battery,” effectively storing excess heat when temperatures are high and releasing it when temperatures drop.

Epic’s four borehole fields contain 6,100 wells total, with the largest field comprising 2,596 boreholes, each 500 feet deep. Two additional closed-loop heat exchanges operate in a 5-acre stormwater pond and a 20-acre retired quarry. The system currently heats and cools nearly half of Epic’s nearly 9 million square feet of building space—a proportion expected to grow with planned expansions. Beyond climate control, the system supplies hot water to Epic’s buildings, and provides heat for underground parking and snow/ice melting on sidewalks.

Analytics for the Next Build

In 2014, during construction of the fourth and largest borehole field, Epic installed groundwater monitoring wells equipped with fiber-optic cables. These sensors collect temperature readings, track water flow and transmit data at 10-minute intervals.

James Tinjun, associate professor at UW-Madison’s Department of Civil and Environmental Engineering, leads the fieldwork with several graduate students. His team’s analyses of Epic’s system have been published in multiple papers, including “Energy Efficiency and Life Cycle Assessment of a District-Scale Geothermal Exchange Unit” in 2023 conference proceedings. Notably, Tinjun determined that Epic’s system operates at an impressive coefficient of performance of 10, which means that one unit of input energy produces 10 units of heating and cooling capacity. According to Epic, each building connected to the GHX system uses approximately 64-percent less energy than comparable commercial buildings.

Epic’s buildings incorporate additional energy-efficient features, including insulated envelopes and green roofs. The campus boasts 41.5 acres of green roofs, which combined with permeable pavement and a zero-tolerance policy on above-ground parking, reduces stormwater runoff and creates a park-like environment. The grounds also include extensive green space, community gardens (for staff to grow their own vegetables) and acres of restored prairie.

Epic is not a typical company. It stores medical records for more than 300 million people worldwide, generates billions in annual revenue and possesses resources beyond most organizations. But I respect a company that’s taking the “sustainable route” with its day-to-day operations though it may have been easier—and cheaper—to do far less.

Leading by Example

Epic plans to install an additional 2,600 GHX wells in 2026, an expansion worth monitoring as construction ramps up. As an engineer, I enjoy studying pioneering projects such as this one that are being tested across the United States and globally. Pilot projects like Epic’s demonstrate how incremental progress and real-world testing can push experimental technologies toward widespread adoption, ultimately moving us toward the energy-efficient and “carbon-free” systems we need.