The whole tussle over berthing cruise ships in downtown Charleston might just come down to an extension cord — a $6 million extension cord zinging enough juice to light up several thousand homes.

It’s also an issue that generates strong opinions about the merits of switching to so-called shoreside electricity to run the big pleasure boats while they’re sitting in port.

And it could come up today, when U.S. District Court Judge Richard Gergel hears arguments on a lawsuit seeking to block a new passenger terminal for Charleston’s cruise industry.

Environmentalists and neighborhood groups allege the project proposed by the State Ports Authority for the north end of Union Pier will bring more tourists, traffic congestion and pollution to the historic district.

Today’s hearing focuses on the validity of a federal construction permit, but opponents to the project are drawing attention to the shoreside power issue by issuing a new study.

The new study from the Coastal Conservation League found that hooking a cruise ship to shoreside power would reduce its emissions by 19 percent to 90 percent, depending on the pollutants, whether or not the ship burns a cleaner fuel that will be required by law.

The SPA, which has resisted calls to install shoreside power, declined to comment on the study. It said Carnival is “operating lawfully in Charleston under all ... emissions standards, adopted by the U.S. EPA for air quality.”

Katie Zimmerman The league’s program manager replied called the group’s study “an expert’s researched report that shows it is worth consideration, and that our decision-makers should not simply dismiss this important solution for pollution mitigation and the reduction of a serious health hazard.”

Asked if the league would withdraw the lawsuit if the SPA agreed to install shoreside power, Zimmerman replied, “We have tried to talk with the SPA about options for reducing the impacts of cruise operations in the past, and our door is always open.”

It costs about $6 million to power a cruise ship if it switches off its engines in port. For an older ship like Carnival’s Fantasy, which is home-ported here, add another $1 million to $2 million.

The Fantasy never has been fitted to use shoreside power but other Carnival ships were under an $200 million upgrade in 2008.

The Coastal Conservation League and the Preservation Society of Charleston are suing the Army Corps of Engineers over a permit it issued for pilings needed to support the $35 million terminal, saying partly that the Army Corps didn’t take into account the effect on historical properties.

The Army Corps and the terminal opponents today will ask Gergel to decide the issue without a trial.

Neither the Army Corps nor the SPA would comment on the litigation.

The suit is the first of three concerning the impact of the SPA’s proposed $35 million cruise ship passenger terminal.

Tyrone Richardson contributed to this report.