The combination of Tesla and SolarCity is already promoting its potential synergies, albeit in a location far away from the mainland United States.
The island of Ta'u in American Samoa is located more than 4,000 miles from the U.S. West Coast, and typically relies on imported diesel fuel to generate electricity.
With no local sources of fossil fuels, Ta'u is in the precarious position of needing periodic shipments of diesel, and facing power outages and rationing when they are delayed.
But this remote island now has an alternative source of power.
A combination of SolarCity solar panels and Tesla Powerpack energy-storage battery packs can now provide nearly 100 percent of Ta'u's electricity, SolarCity says.
This "microgrid" consists of 1.4 megawatts of solar-generation capacity from SolarCity, and 6.0 MWh of energy-storage capacity from the Tesla Powerpacks, according to a SolarCity blog post.
Tesla and SolarCity solar farm on Ta'u, American Samoa
The project was completed in less than a year, with funding from the American Samoa Economic Development Authority, the U.S. Environmental Protection Agency, and the Department of the Interior.
Use of energy-storage battery packs was crucial to supplying enough power to satisfy the needs of Ta'u's roughly 600 residents.
Energy storage allows excess electricity harvested by solar panels to be used later, when sunlight isn't available.
This ensures that energy harvested during the day does not go to waste, and that electricity is available consistently.
Renewable energy is also a particularly attractive option for islands, which usually lack local sources of fossil fuels and the infrastructure to connect their electricity grids to the mainland.
As well as the Samoan installation, which will be operated by American Samoa Power Authority, Tesla and SolarCity announced plans earlier this year for a solar farm and energy-storage array on the Hawaiian island of Kauai.
Tesla and SolarCity energy storage array on Ta'u, American Samoa
Even before Tesla's acquisition of SolarCity was approved by shareholders last week, the two companies were closely affiliated.
Tesla CEO Elon Musk already sits on SolarCity's board and his cousin, Lyndon Rive, runs the company.
The acquisition of SolarCity by Tesla was widely criticized by analysts as a distraction for the electric car company, and financially disadvantageous.
Nonetheless, excluding votes by Musk and others affiliated with SolarCity, holders of 85 percent of Tesla shares voted for the acquisition, according to the carmaker.