(Reuters) - SolarCity Corp <SCTY.O> said on Wednesday it was disappointed with a decision by Nevada regulators to exclude the company from a proceeding to decide how existing customers would be compensated for the excess energy their rooftop solar panels sent back to the power grid.

Nevada's Public Utilities Commission had voted unanimously in February to require households with solar panels to move to a new, less generous rate structure.

NV Energy [VNEN.UL], a Nevada utility owned by billionaire investor Warren Buffett's Berkshire Hathaway Inc <BRKa.N>, asked the commission in July to maintain previous rates for customers with solar systems installed before Dec. 31, 2015. SolarCity last week requested permission to take part in the proceeding on whether or not to grandfather these customers.

No other solar companies have sought to intervene, according to documents filed with the commission.

The commission on Monday denied SolarCity's request, saying its customers were adequately represented by the state's Bureau of Consumer Protection.

It added that the outcome of the proceedings would not affect SolarCity's existing contracts.

SolarCity said in a statement that the commission's decision deprived Nevada solar customers of the chance to help decide policies that affect them.

(Reporting by Nichola Groom; Editing by Richard Chang)