Borrego Solar Systems Inc., a San Diego designer, installer and financier of solar energy systems, said it closed a $64.4 million fund for solar projects, receiving the investment from US Bank and National Cooperative Bank.

The latest round of investment is the largest for the company since the firm began offering power purchase agreements in 2009, and brings the total amount of capital raised to $225 million, the company said.

The money will be used to build more than 18 megawatts of solar systems in eight projects including four landfills and one school district.

Borrego Solar designs, builds and operates the systems, and sells back the energy generated to the customers at reduced rates. The arrangement allows customers to reduce their electric bills without having to pay high upfront costs involved in building and operating the systems, the company said.

Minneapolis-based US Bank is an earlier investor in Borrego, while National Cooperative Bank is based in Washington, D.C.