US-based start-up Last Energy has completed a Series C funding round at $100m, led by Astera Institute with participation from AE Ventures, Galaxy Fund, Gigafund, JAM Fund, The Haskell Company, Ultranative, Woori Technology, Galaxy Interactive and other investors.
Last Energy is developing a high-pressure water-cooled reactor design, based on an established solution. The initial project for a pressurised water reactor (PWR) was developed for NS Savannah – the world’s first nuclear-powered merchant ship.
In August 2025, the company was selected for the US Department of Energy’s (DOE) Reactor Pilot Program. Leveraging a previously procured full core load of fuel, Last Energy secured a lease at the Texas A&M-RELLIS applied research campus and signed the first known Other Transaction Agreement (OTA) between DOE, further supported by its recognition in the Atlantic Partnership for Advanced Nuclear Energy.
In October 2025, Texas A&M University System and Last Energy agreed to collaborate on the deployment of a pilot microreactor at Texas A&M-RELLIS. The pilot will feature Last Energy’s PWR-5 reactor, a scaled down version of its commercial PWR-20 design.
In the United Kingdom, Last Energy has completed a Preliminary Design Review and is the only known company with a regulator-confirmed pathway toward a potential 2027 site licence decision.
“We believe this financing will fully capitalise us through our DOE pilot project and position us to transition into commercialisation of our production power plants,” said Last Energy Founder and CEO Bret Kugelmass. “A new nuclear era is underway, and we intend to showcase how factory fabrication will unlock the scalability that the energy market demands.”
Following this latest funding round, Last Energy is focusing on completing its PWR-5 pilot reactor, advancing PWR-20 commercialisation, and strengthening its footprint in Texas through expanded investment in manufacturing capabilities and partner engagement. The company plans to bring the pilot reactor online next year, and to bring the 20 MW serial unit into production in 2028.
Last Energy aims for its Texas A&M project to go critical by mid-2026, according to Last Energy’s Vice President, Commercial Development Adam Lenarz. This is a very ambitious target but is in line the DOE’s goal to have at least three projects in its pilot programme achieving criticality by 4 July 2026. This follows the Executive Order signed by President Donald Trump in May 2025, Reforming Nuclear Reactor Testing at the Department of Energy.
