Why Elon Musk Wants to Take SolarCity Under Tesla's Wing

Musk is the biggest shareholder in both public companies.

"This is something that should happen," Musk said during a conference call with reporters Tuesday, calling the all-stock deal, which is valued at about $2.8 billion, a "no-brainer."

Musk and Antonio Gracias, a Tesla director who also sits on SolarCity's board, will sit out of the vote on whether Solar City should be sold to Tesla.

SolarCity shareholders seemed pleased with the news, with the company's stock up 16 percent, to $24.50 in after-hours trading after the announcement.

The Associated Press contributed to this report.