The Germany-headquartered business was set up by the pan-European direct investor Omnes.
Following the credit agreement, ILOS Projects will seek to deliver solar and battery-driven energy projects to inject more than 2,000 MW of electricity into distribution grids by 2026.
The company was founded in 2018 and is initially targeting solar power developments in Ireland, the UK, the Netherlands, Greece and Italy.
EIG's credit agreement also provides scope for diversification in energy production longer term, potentially delivering co-located battery storage and hydrogen facilities across OECD territories. The loan capital will provide both construction equity as well as acquisition capital that can be leveraged to buy "ready-to-build" assets.
The financing is divided into two equal tranches of €250 million, with the first payment expected to be actioned imminently. The second tranche is accessible through an accordion to increase lending by an additional €250 million if needed.
Michael Pollan, partner at Omnes, said: "ILOS has seen tremendous growth over the last two years.
"We are proud to continue supporting the company as it works toward this ambitious IPP project.
"We also look forward to partnering with EIG, a leader in the energy infrastructure sector that shares our common values and strategic view."
Rob Johnson, managing director and global head of direct lending at EIG, added: "We're thrilled to support ILOS in these exciting growth initiatives as they work to expand their footprint across Europe.
"This transaction is a testament to our confidence in the management team, their strategy and ILOS's sponsors, and it underscores EIG's commitment to investing in high-quality assets and energy infrastructure that support a low-carbon future."