Geothermal Cooling for Data Centers: Your Top Questions, Answered

October 27, 2026

Geothermal cooling gives data centers a proven, predictable way to reject heat into the earth — without touching groundwater. As more operators look beyond conventional cooling, we hear the same questions again and again. Here are the answers, in one place.

What type of geothermal is this?

This is Borehole Thermal Energy Storage (BTES) — geothermal for cooling and heating, not for generating electricity. When most people hear “geothermal,” they picture power plants tapping steam miles underground. BTES works at a fraction of that depth, cost and geographic constraint.

A typical single borehole runs about 850 ft deep and 7 in. wide. A PE100 (HDPE) U-tube carries water down and back up, surrounded by grout, transferring heat to the surrounding earth.

Is geothermal technology proven in data center applications?

Yes. Closed-loop geothermal is installed in more than 100,000 buildings in the U.S. and over 1 million worldwide. Its performance is proven and predictable.

Brightcore engineers and scientists have designed more than 50 geothermal-cooled systems for data centers across Europe, serving telecom, broadcast and streaming, and government sites.

In the U.S., Brightcore has deployed its hybrid cooling management approach on traditional buildings with cooling-dominant or heating-dominant loads. In those projects, conventional HVAC equipment such as dry coolers works alongside the borefield to keep it thermally balanced.

Does this solution impact underground water?

No. BTES has no interaction with groundwater. It’s one of three general types of underground thermal energy storage, and the only one that keeps water fully sealed inside a closed loop.

Borehole Thermal Energy Storage (BTES)

• Boreholes 500–1,000 ft deep, drilled into rock or soil
• Water circulates through closed-loop piping to reject heat into the earth
• No water or fluid is exchanged with the ground or groundwater
• No water rights, no aquifer permitting, and no dependence on whether the site sits on a usable aquifer
• Performance is predictable and designable in advance, because you engineer the borehole field rather than characterize an unknown subsurface water body

Aquifer Thermal Energy Storage (ATES)

• Boreholes drilled into an underground aquifer — shallow formations of permeable rock that fluid can travel through
• Groundwater is pumped in and out of the natural aquifer to reject heat
• Limited to geographies with aquifers that have enough heat rejection capacity
• Performance depends entirely on local hydrogeology, which varies site to site and isn’t fully knowable until test wells are drilled
• Requires water rights, well permits and often groundwater quality monitoring, adding regulatory timeline and site-specific risk
• Often needs fewer boreholes and benefits from natural groundwater flow when conditions are good — but when they’re not, there’s no fallback

Reservoir Thermal Energy Storage (RTES)

• Uses permeable reservoirs at XX–XX ft, including depleted oil and gas formations
• Similar to ATES, but with higher upfront characterization costs and longer lead times before you know whether a site works
• The least commercially mature of the three: most RTES literature is still research-stage (USGS and DOE pilots), not commercial deployment at data center scale

The bottom line

BTES requires more boreholes, but it delivers a known, repeatable number — which makes it scalable across the entire data center industry. ATES and RTES may need fewer boreholes when groundwater flow and capacity are favorable, but that isn’t guaranteed at every site. Performance fluctuates as groundwater changes over time, and permitting complexity adds significant risk, making them less likely to scale to every data center location.

How are geothermal projects permitted?

In most locations, BTES permitting generally falls under water well permits, and permits are typically procured within weeks to months. Engaging early with local planning staff is key to understanding specific requirements and any potential hurdles for a project at data center scale.

How big is the borefield?

In most data centers modeled, the borefield fits within the facility’s footprint. Exact size depends on several factors, including:

• Subsurface ground temperature
• Outdoor air temperature
• Operating fluid temperatures
• The equipment paired with geothermal

Systems are standardized in construction but sized to each data center and the customer’s design goals.

How can space above the borefield be used?

Most typical site infrastructure can be built above the borefield with planning and coordination. Buried piping sits with the top of pipe at least four feet below finished grade or below the frost line, whichever is deeper. That places the borefield below the zone affected by most surface construction.

Buildings, power switchyards, battery storage, parking lots and landscaping can all coexist with the borefield. The table below rates the coordination effort for each.

What type of data center cooling does geothermal work for?

Geothermal cooling works with both the technology loop and the whitespace loop, and it’s compatible with all chip temperatures.

It delivers its highest efficiency gains at high temperatures. For lower-temperature applications, the system can still be installed today. If higher-temperature compute is added later, the borefield’s capacity increases along with it — so the infrastructure scales with your compute roadmap instead of needing to be replaced.

Have another question?

Every data center is different, and the right geothermal design depends on your site, your loads and your compute roadmap. Reach out to the Brightcore team to talk through your project.