The archive · Climate & Energy · Strategic decision · 2019–2026
Last Energy's steel-cased reactor bet: $100M Series C, 5MW Texas A&M pilot due 2026
Bret Kugelmass's Last Energy raises $100M to build a 5MW pilot at Texas A&M and mass-produce 20MW PWR-20 micro-nuclear plants for data centers.
Last Energy
What the business is
Last Energy builds the PWR-20, a 20-megawatt pressurized-water micro-nuclear plant designed for factory fabrication and rapid on-site assembly, targeting data centers, heavy industry and defence installations.
Starting capital：$100M Series C led by Astera Institute (Dec 2025); $40M Series B in 2024 brought total to $64M (ESG Today)
How it started
Kugelmass founded Last Energy in 2019 in Washington, D.C., after years of trying to convince people nuclear mattered, betting that small reactors could be built like manufactured products rather than one-off megaprojects. Instead of courting utilities, the company went after private industrial and data-center buyers, and chose a proven pressurized-water reactor lineage to keep licensing risk low.
What happened
In 2024 Last Energy closed a $40M Series B (total $64M), signed agreements for 80 units — 39 of them for data centers — and set a goal of 10,000 units in 15 years. By February 2025 it had secured a Texas site for 30 microreactors; in September 2025 it signed an £80 million, subsidy-free agreement with DP World to build its first unit at London Gateway, after the UK's ONR completed a preliminary design review of the PWR-20 in June 2025. In December 2025 a $100M Series C led by Astera Institute fully funded a 5MW pilot reactor on a site leased from Texas A&M, with startup hoped for in 2026 and 20MW commercial production in 2028.
How it ended up
Still running: the Texas A&M pilot is fully funded and under development, 80+ unit agreements stand, but no Last Energy reactor has yet generated power.
Background
Last Energy is a Washington, D.C.-based startup founded in 2019 by Bret Kugelmass to build the PWR-20, a 20-megawatt pressurized-water micro-nuclear plant made of modules that snap together like a LEGO kit and can be fabricated, transported and assembled within 24 months. It targets private industrial facilities and data centers that cannot wait a decade for gigawatt-scale nuclear.
The company's bet is that nuclear can be treated as a manufactured product rather than an infrastructure project: factory-fabricated cores, private financing with no subsidies, plants owned and operated on customers' sites to avoid grid-upgrade pipelines, and cores permanently encased in steel that doubles as the disposal cask. The design descends from a US-government reactor built for the NS Savannah in the 1950s, which Kugelmass argues short-circuits licensing and fuel-supply risk.
Last Energy closed a $40M Series B in 2024, signing agreements for 80 units with 39 earmarked for data centers, then expanded in Europe: an £80 million first-unit agreement with DP World at London Gateway (September 2025), following the UK regulator's preliminary design review in June 2025. In December 2025 it raised a $100M Series C led by Astera Institute to fully fund a 5MW pilot reactor on a site leased from Texas A&M, targeting startup in 2026 and 20MW commercial production in 2028.
As of September 2026 no unit has operated. The company's stated ambition — 10,000 units in 15 years — hinges on the pilot reaching criticality and on UK licensing concluding by the end of 2027, making the first unit the real test of the mass-manufacturing thesis.
What has to be true
- Targets private industrial and data-center buyers who cannot wait for gigawatt plants, betting a 20MW unit can be deployed on an existing site in about 24 months.
- Owns and operates plants on customer property, bypassing transmission-grid expansion and utility procurement cycles — the usual decade-long delays.
- Reuses the proven pressurized-water reactor design from the NS Savannah to cut licensing and fuel-supply risk versus novel SMR designs.
- Frames nuclear as a manufactured product at fleet scale — 10,000 units in 15 years — with steel-encased cores eliminating refueling, servicing and separate waste disposal.
What can be applied
A proven design plus a productized, privately financed model can raise hundreds of millions before a single watt flows — but the fleet bet pays off only when the first reactor actually runs.
Aftermath
As of 2026-09-02, Last Energy's 5MW pilot reactor at the Texas A&M site is fully funded by the December 2025 Series C and targeted for startup in 2026, with the 20MW PWR-20 entering production in 2028. The DP World London Gateway project, described as the company's first unit, aims for operations around 2030 pending UK licensing expected to conclude by the end of 2027. The company still lists more than 80 commercial agreements, but no unit has yet generated power, so the manufacturing-and-licensing thesis remains unproven.
Sources
- Nuclear startup Last Energy raises $100M for its steel-encased micro reactor
- Last Energy Partners With DP World To Bring Micro-Nuclear Power To London Gateway
- Micro-Nuclear Power Plant Startup Last Energy Raises $40 Million to Decarbonize Heavy Industry and Data Centers
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