The "Next-Generation Geothermal Research and Development Act" aims to significantly advance geothermal energy by amending the Energy Independence and Security Act of 2007. This legislation directs expanded research, development, demonstration, and commercial application activities for next-generation geothermal systems , particularly focusing on those operating in various conditions, including supercritical environments. It introduces new definitions to the existing law, such as "closed-loop geothermal systems" and "supercritical conditions," to encompass a broader range of advanced geothermal technologies, including enhanced geothermal systems and those operating in supercritical conditions. A key provision establishes a new Next-Generation Geothermal Research and Development Program within the Department of Energy's Geothermal Technologies Office. This program will specifically support research into supercritical geothermal, covering topics like well completion, reservoir management, materials development, and sensor technology. The Secretary of Energy is directed to award milestone-based grants for deep drilling projects in unique geodynamic settings, progressing from characterization to power production. Additionally, the bill mandates that at least one FORGE site be capable of testing next-generation geothermal systems in supercritical conditions within one year of enactment. The bill enhances data sharing by requiring the geothermal drilling data repository to include publicly available subsurface data from fossil fuel and mining operations, with periodic updates for standardization and accessibility. It also mandates a memorandum of understanding between the Secretaries of Energy and Interior to facilitate data sharing, prioritizing heat, lithology, and strain profiles from deep exploration boreholes. Furthermore, the Secretary of the Interior is tasked with commissioning regional deep data probes , drilling boreholes deeper than 8 kilometers to provide control points for deep heat mapping. The legislation also establishes a Next-Generation Geothermal Center of Excellence through competitive grants to National Laboratories, universities, or partnerships, tasked with advancing R&D, fostering collaboration, and supporting workforce development. The bill introduces two new grant programs: Commercial-Readiness Innovation Grants to accelerate the development and testing of innovative technologies for enhanced and closed-loop geothermal systems, and Next-Generation Geothermal Systems Surface Facility Innovation Grants for improvements in the operation, cost, and design of surface components. Priority for these grants is given to projects advancing near-term commercial deployment, especially in diverse geological or supercritical conditions. Finally, the legislation requires updated national geothermal resource assessments, including quadrennial updates and initial assessments of next-generation and supercritical geothermal resources within two and five years, respectively, to better understand the nation's geothermal potential. Appropriations of $5,000,000 are authorized for fiscal years 2027 through 2031 for the enhanced and closed-loop geothermal systems research, development, and testing subsection.