SINGAPORE – Temasek-backed fusion company Commonwealth Fusion Systems raised US$1 billion (S$1.29 billion) in its latest funding round, taking total capital raised to US$4 billion to drive its efforts to commercialise its nuclear power technology.
In a July 30 announcement, the US company said investors included pension funds, sovereign wealth funds, and infrastructure and industrial corporate partners.
Commonwealth Fusion, which has attracted the most funding among fusion developers globally, declined to name the investors.
The latest funding raise is among the largest for the global fusion industry, which has been making rapid advances in designs and materials towards commercial fusion power.
Fusion energy seeks to harness the same process that powers the sun to create a clean and almost limitless source of energy and meet growing demand for electricity.
Fusion energy combines lightweight atomic nuclei – typically hydrogen isotopes, deuterium and tritium – to form heavier ones, releasing massive amounts of energy with minimal long-lived radiation and no risk of nuclear meltdowns.
It is different from fission energy used in large nuclear power plants, which involves splitting atoms and releasing large amounts of radiation.
Harnessing fusion energy requires systems that can withstand temperatures of 100 million deg C or more and immense pressures for long periods.
The idea is to create self-sustaining fusion reactions within a super-hot plasma and capture the heat to generate electricity.
But perfecting the design of the reactors and the materials has been fiendishly difficult, and there are 56 private-sector fusion start-ups globally working to achieve commercially viable machines, according to Washington-based global advocacy group Fusion Industry Association.
High levels of investor interest in fusion energy has hastened development.
Commonwealth Fusion has become the leading US firm and accounts for about 30 per cent of all funding raised by global private fusion developers to date, chief executive Bob Mumgaard said during a conference call.
“We think that fusion is emerging as a next big thing in energy, but also a next big thing in tech,” he said.
Temasek was an early investor in Commonwealth Fusion, leading a Series A2 round in 2020 that raised US$84 million. It also participated in a US$1.8 billion Series B round in 2021 and made a follow-on investment in the 2025/26 financial year.
It declined to confirm if it took part in Commonwealth Fusion’s latest round of funding.
Temasek has also invested in Canada’s General Fusion, which is perfecting its own plant design with the aim of a commercial power plant around 2035.
Mumgaard said that SPARC, Commonwealth Fusion’s flagship demonstration plant in Devens, Massachusetts, was about 80 per cent complete. It expects the plant to produce more energy than it consumes by 2027.
The firm, also backed by Google, Nvidia and others, plans to quickly take the lessons learnt from SPARC and start building its ARC commercial power plant in Virginia, with completion in the early 2030s. Google has already signed a deal to take half the plant’s electricity.
Mumgaard said the latest funding will help accelerate plans to develop ARC.
“We’re going to put that to work on getting ready for ARC. So this goes to commercialisation efforts,” he said.
A focus will be building up supply chains and partners and ensuring the key technologies are ready, “so that as when we turn on SPARC, we can go very quickly afterwards to ARC”.
Singapore is exploring a range of low-carbon energy technologies to power the nation’s future, including fusion and conventional nuclear power, including small modular reactors.
The country could become an anchor for fusion energy in the region, Mumgaard told ST on the sidelines of Ecosperity Week 2026, Temasek’s flagship sustainability summit, in May.
He pointed to Singapore’s strong research ecosystem, industrial high-tech community, strong regulatory and investment environment, and its ability to develop and put in place long-term development plans.
“Singapore is a model system for what a future fusion-powered urban society could look like,” he said after signing a collaborative research agreement with A*STAR.
But there’s still much to be done to prove fusion energy can be commercialised to be reliable and affordable.
“We’re working on something very hard right now that we used to think was impossible. Now it’s feeling more and more inevitable. And at the same time, we’re getting ready for the next stage,” Mumgaard said on the conference call.
