Institutional Shareholder Services (ISS), following an examination of Tesla Motors and SolarCity , recommends in favor of Tesla's acquisition of SolarCity. "The transaction is a necessary step towards TSLA’s goal of being an integrated sustainable energy company," said ISS, an influential proxy advisory firm that recommends votes for contested situations and deals to institutional shareholders. "Additionally, it appears reasonable to assume that TSLA is paying a low to no premium to take over SCTY."

The combined company will become the world's only integrated sustainable energy company, ranging from clean energy generation to storage to transportation, resulting in a better outcome for shareholders, customers and the environment.

The more than $2 billion deal has faced pressure from shareholders critical of the takeover plan, given the performance struggles at SolarCity and Tesla founder Elon Musk's prominent role at both companies.