By Patricia Hurtado - Mar 21, 2013 9:50 AM ET

NextEra Energy Capital Holdings Inc., a unit of NextEra Energy Inc. (NEE) (NEE), sued banks including Banco Bilbao Vizcaya Argentaria SA (BBVA) to clarify its financing obligations to solar power projects in Spain.

NextEra Energy, the largest U.S. wind-power operator, sued 16 banks yesterday in Manhattanfederal court, asking a judge to interpret a 2011 credit “guarantee agreement” in light of recent changes in Spanish law.

NextEra said Spain enacted favorable tariff laws in the 1990s to encourage investment in solar power so that by 2008, the country accounted for more than 40 percent of the world’s solar installations.

Those tariff laws were changed in December, directly affecting NextEra’s obligations under the guarantee agreement, the company said. The changes trigger a limit on NextEra’s base equity contribution to the projects, the company alleged in its complaint.

The banks, which provided financing for the projects, dispute the company’s interpretation of the agreement, NextEra said. NextEra asked the court to find that the change of law caps its obligation under the agreement.

NextEra, based in Juno Beach, Florida, fell 31 cents to $75.39 at 9:46 a.m. in New York Stock Exchange composite trading. The shares had gained 9.4 percent this year before today.

The case is NextEra Energy Capital Holdings Inc. v. Banco Bilbao Vizcaya Argentaria SA (BBVA), 13-cv-01873, U.S. District Court, Southern District of New York (Manhattan).

To contact the reporter on this story: Patricia Hurtado in New York atpathurtado@bloomberg.net

To contact the editor responsible for this story: Michael Hytha at mhytha@bloomberg.net