(Adds detail on investments, background)
By Hadeel Al Sayegh and Stanley Carvalho
ABU DHABI, Feb 13 (Reuters) - Saudi Arabia's Public Investment Fund (PIF) plans to increase its stake in ACWA Power IPO-ACPO.SE to 40 percent from 25 percent and is looking to invest in electric vehicles and solar power, its managing director said on Wednesday.
The sovereign fund also plans to boost its staff to 700 by the end of the year from 450 now, and is aiming to open offices in London and in the United States - initially in New York and then in San Francisco, Yasir al-Rumayyan told a conference in Abu Dhabi.
"We will be the largest investor in renewable energy," he said. "Oil, we think, is very important to us, we don't want to waste oil only on transportation."
The fund has made substantial commitments to other green projects, including renewables and recycling, and to technology companies, such as a $45 billion agreement to invest in a technology fund led by Japan’s SoftBank Group Corp. It also owns stakes in electric car makers Tesla and Lucid Motors.
PIF is also backing the country's plans to diversify into solar power as well as waste management, infrastructure and entertainment.
The fund, which has $360 billion in assets according to the Sovereign Wealth Fund Institute, is also an investor in ride-hailing firm Uber Technologies, which he said at $3.5 billion was its largest private equity investment.
In October, Saudi Crown Prince Mohammed bin Salman said PIF will surpass its target of increasing its assets to $600 billion by 2020.
Rumayyan said Uber brought more than 150,000 jobs to Saudi Arabia, mainly for young citizens.
"That is what we are trying to do with our other (international) investments," he said "We are bringing back some of these companies to Saudi to improve our domestic economy." (Additional reporting by Marwa Rashad; Writing by Saeed Azhar; Editing by Louise Heavens)