Last Energy
🇺🇸 Austin, US · Founded 2019 · Active
Last Energy is a US nuclear company founded in 2019 and headquartered in Austin, Texas, since moving from Washington, D.C., in May 2025. It designs the PWR-20, a 20 MWe (80 MW thermal) pressurised water reactor that uses standard low-enriched uranium fuel and is built in factory modules. It plans to build, own and operate its plants and sell the power to data centres and industrial sites under long-term contracts. In December 2025 it announced a pilot of a 5 MWe version, the PWR-5, at Texas A&M University's RELLIS campus, a project the Department of Energy selected for its reactor pilot programme, alongside a plan for 30 microreactors in Haskell County, Texas. It has also announced projects in Wales, Poland and Romania. None of its reactors has been built.
- Sector
- Fission
- Technology
- Pressurised water reactor
- Fuel
- Low-enriched uranium
- Role
- Reactor developer
Its recorded equity, $140m, is the 14th largest of the 25 organisations with a priced round here. Not every round is on record, so this is not its total raised.
Terms
- Pressurised water reactor
- Ordinary (light) water kept under high pressure so it heats without boiling, transferring heat to a separate steam loop; the water is both coolant and moderator. Fuel is low-enriched uranium oxide pellets in zirconium-alloy rods. The most common reactor type in service worldwide.
- Low-enriched uranium
- Uranium enriched to 5% uranium-235 or less, typically 3 to 5%: the range almost all power reactors use. Formally, anything below 20% is low-enriched; this site holds the band from 5% to just under 20% separately as HALEU, with its 5 to 10% part also tagged as LEU+. A fuel above 5% uranium-235 belongs in one of those, never here, whatever a developer's own materials call it.
Funding
- 2025-12-16Equity round · Series CSeries C of "more than $100 million", announced as closed on 16 December 2025, led by the Astera Institute.$100m
- 2024-08-29Equity round · Series BSeries B of $40 million announced 29 August 2024, closed earlier in 2024, led by Gigafund. The release's "total capital raised to $64 million" is cumulative and not a deal.$40m
Designs
| Design | Developer | Approach | Electrical output per unit | Size class | Licensing stage |
|---|---|---|---|---|---|
| PWR-20 | Last Energy | Pressurised water reactor | 20 MWe planned | Small modular reactor | No milestone recorded |