National Grid is also committing to better understanding "the transformation occurring in the sector", and is set to work with Sunrun to "explore options of how distributed energy resources might be aggregated and used to help keep the energy grid balanced and optimized".
A new company is to be set up to take on the system operator (SO) duties of National Grid, separating it from the transmission operator (TO) in an effort to address perceived conflicts of interest and prepare for future changes in the UK's energy system.
But energy regulator Ofgem will separate the two arms of the company, rather than breaking it up.
National Grid charges power companies to transport electricity and ensures enough supply.
The new company's board members won't be able to sit on the National Grid group board or other National Grid electricity company boards, it added.
The restructuring is expected to cost National Grid £46.5 million with annual costs of £6.5 million and could see some costs passed to industry.
National Grid owns and operates key parts of Britain's energy infrastructure.
But it also balances supply and demand across the network.
On Tuesday, Sunrun announced the partnership with National Grid, one of the world's largest investor-owned utilities, which serves more than 20 million people in the USA, as well as running the grid in the United Kingdom.
This news was "slightly positive", RBC analysts said in a research report Thursday as the "earnings and asset base relating to the system operator role will remain with National Grid and contribute towards its bottom line".
Attention has focused upon National Grid's role in developing interconnector cables to import power from overseas.
But authorities stopped short of spinning the operating entity completely off from National Grid, meaning profits from the operator will continue to be consolidated into the wider group. "It is time for it to be brought to these shores".
"We are excited to partner with National Grid, a utility focused on truly creating a clean energy future, and to promote the growth of rooftop solar in the United States", said Lynn Jurich, Chief Executive Officer of Sunrun.