Elon Musk’s Tesla offered to acquire California-based SolarCity, Tuesday. Tesla’s board of directors sent SolarCity an offer on Monday to acquire all of the firm’s outstanding shares, and common stock.

Tesla’s current proposal offers to purchase SolarCity’s shares at $26.50 to $28.50 per share,

SolarCity is one of the largest solar providers in Arizona, with multiple locations across the valley and the state.

Tesla launched Tesla Energy in 2015, which provides PowerWall and Powerpacks to homeowners, which are batteries that can store solar energy in a home.

Tesla sees the offer as completing its “picture” of providing sustainable solutions, from its popular cars to its renewable energy storage efforts.

“We believe that the possibilities for product, service and operational synergies would be substantial, and that a combination would allow our companies to build on our respective core competencies and remain at the forefront of delivering innovative approaches for sustainable transportation and energy,” Tesla said in its offer to SolarCity.