Tesla Motors now owns the nation's largest solar panel installer.
Tesla's deal to acquire SolarCity Corp. closed Monday morning.
Shareholders of both companies approved the deal last week by wide margins.
The all-stock deal valued SolarCity at $2 billion based on Tesla's closing stock price Friday. It was worth $2.6 billion when Tesla and SolarCity announced the agreement in August, but their share prices have dropped since then.
Tesla CEO Elon Musk — who is also chairman of SolarCity — wants to sell solar panels through Tesla's stores. Customers can buy them to power their homes and charge their Tesla electric vehicles.
Musk says the companies' first joint product — solar roof tiles that look like traditional tiles — should be ready for installation by next summer.