Heating and cooling (HVAC), and refrigeration represent roughly a third of global energy use, yet most of that demand is still served by fossil fuels. And as electricity demand rises and grids get tighter, thermal is becoming a reliability and cost issue, not just a climate one.
That is why we invested in Dig Energy, a company making geothermal heating and cooling dramatically easier and cheaper to deploy by reinventing how shallow drilling gets done.
The bottleneck: drilling
Ground-source geothermal is one of the best tools we have to decarbonize buildings and reduce peak demand. The ground stays at a stable temperature year-round, which makes geothermal heat pumps highly efficient and resilient across seasons.
But geothermal has not scaled because its biggest input, drilling, is still too expensive, too slow, and too operationally complex for most commercial projects. In many installs, drilling is the dominant cost driver, and it adds schedule risk, contractor coordination challenges, and site constraints that can derail otherwise compelling economics.
In short: the technology works; the economics often do not.
Dig’s breakthrough: affordable, efficient, fast drilling
Dig has built a compact, purpose-built drilling system for shallow geothermal designed to reduce the steps, time, and cost of installation. Their approach is designed for the realities of commercial deployment: constrained sites, repeatable operations, and a workflow that can scale beyond a small set of highly specialized contractors.
Dig is not trying to convince the world geothermal is valuable. They are removing the reason it has stayed niche.
Why now, and why Dig
What makes us especially excited is the team. Co-founders Dulcie and Thomas pair strong technical depth with a pragmatic, field-first mindset. They are doers – building for real sites and real timelines, not idealized installs.
That mindset shows up in where they are starting. Dig is focused on customers where heating and cooling is a real line item and where upgrades can be justified by economics, not just sustainability goals: commercial facilities, retail-scale sites, and campuses.
This timing matters. Utilities are increasingly constrained during peak seasons, electrification is pushing demand upward faster than capacity expansion, and building and corporate decarbonization requirements are tightening. Building owners are looking for solutions that lower bills, cut emissions, and reduce exposure to peak pricing and reliability events.
Geothermal is uniquely positioned because it can do all three, but only if it becomes affordable and scalable.
Dig is enabling that shift with an approach built for deployment: performance in the field, manufacturability, and repeatable rollout. This is not a science project. It is infrastructure execution.
We believe Dig can help make geothermal a mainstream tool for building decarbonization and grid resilience, not a niche option reserved for the handful of projects that can afford high drilling costs and complexity.
We are proud to back Dulcie, Thomas, and the Dig Energy team as they build the future of clean thermal. We are also excited to invest in the Seed round alongside great co-investors, including Avila, Azolla, and Baukunst.
Dig is one of Sunna’s investments in the energy and grid space. We’ve also recently backed Magnefy and Unblock, with more to share soon.