The project was projected to cost $200 billion through 2030.
Reports suggest that SoftBank is probing what could be a shareholder-led smear campaign against two of its executives - Nikesh Arora (one-time heir apparent to SoftBank CEO Masayoshi Son) and Alok Sama (now the company's chief strategy officer).
The project is so enormous that it could take over a full decade to complete.
"This kind of a project would never have been feasible without the big vision we shared with the crown prince", Son told reporters. "But most importantly it has the greatest vision".
The deal was signed on the sidelines of a U.S. visit by Saudi Crown Prince Mohammed bin Salman, who has undertaken a whirlwind of economic and social reforms. It will reach its maximum capacity by 2030 and may cost close to $1 billion per gigawatt. Son called the solar project the world's biggest.
SoftBank's Son added that the electricity produced in the first phase will be sold and that would help financers to earn money for the forthcoming stages.
In its latest efforts to increase access to renewables and reduce dependence on oil, Saudi Arabia has drawn up plans to build the world's biggest solar farm, which, if realized, would create 100,000 jobs in the oil-rich kingdom and produce 200 gigawatts (GW) of energy, a third more than the global photovoltaic industry supplied worldwide a year ago. The country can shave off $40 billion power bills, he said as quoted by Bloomberg.
The announcement happened during the NY leg of Prince Mohammed's trip across the United States. A factory unit is being planned in the kingdom to manufacture the panels locally. It was announced in NY after a Saudi-U.S. CEO forum held on the sidelines of the crown prince's multi-day tour across the U.S.
Saudi Arabia's Public Investment Fund is the largest investor in Softbank's $100 billion Vision Fund. Saudi Arabia's sovereign wealth fund, the Public Investment Fund, which has more than US$224 billion in assets, spent about US$54 billion on investments a year ago.