Oil major Chevron Corp. said Aug. 12 it is investing in Zap Energy Inc., joining Italy's Eni SpA and Norwegian state oil company Equinor ASA who have also backed nuclear fusion startups to reduce their carbon footprint.

Chevron's decision comes as energy companies face increasing pressure from investors to reduce emissions, spend more on low-carbon energy and disclose the impact of their fossil fuel production on climate change.

"Chevron Technology Ventures' investment in fusion is an opportunity to enhance the company's focus on a diverse portfolio of low-carbon energy resources," Chevron said in a statement, without putting a number on the size of its investment.

Nuclear fusion is a process that releases large amounts of energy with no greenhouse gas emissions and limited long-lived radioactive waste.

Zap Energy raised $6.5 million from its Series A financing on July 12, according to data from Crunchbase.