EDITORIAL Over the next few weeks, the Board of Supervisors will be looking at two major electric-power programs that could add a lot of new generation capacity (and possibly new pollution) to southeast San Francisco and a new source of backup power from out of town. Both projects seem to have broad support at City Hall.

The main questions that city officials ought to be asking about plans for a new power plant in Potrero Hill and a new power cable to bring electricity across the bay are:

•Do we really need either?

•What is motivating the powerful but little-known state agency to demand that San Francisco — the only US city with a federal public power mandate — prepare for a future in which energy use continues to grow, conservation lags, the private sector controls the city's power supply, and the city's plans for cutting power use are a failure?

The California Independent System Operator, known as Cal-ISO, was created in the wake of the wretched energy deregulation plan that the State Legislature concocted in 1996. The outfit, run by a five-member board appointed by the governor, is supposed to ensure that every part of California has enough electricity — now and in the future.

But the board members are almost all former utility executives, including a retired Pacific Gas and Electric Co. official, and like most utility executives, they seem to believe that the only track for electricity use is upward.

So Cal-ISO has informed San Francisco that it doesn't have enough power on hand to make it through 2010. That means the city needs to either find a new way to import more power (the only significant current pathway is a cable that runs up the Peninsula and is owned by PG&E) or build more power plants inside its limits.

The problem with building more plants, particularly the kind of plants Cal-ISO likes — fossil fuel burners that can run day and night without interruption — is that San Francisco residents are trying to get rid of the last big polluting plant, Mirant Corp.'s facility at the foot of Potrero Hill, not build more.

So the latest solution involves the installation of three natural gas–<\d>fired generators known as peakers, which would run only when demand is high and other sources (including the solar facility the city plans to build) aren't operating. The mayor and the supervisors are referring to these plants as "city-owned generation," making this sound like a big step on the way to public power.

And on one level, it is: San Francisco won the turbines (which are essentially big jet engines) as part of a settlement with Williams Energy after the energy crisis, and they could be part of a municipal utility. But the current plans call for the Chicago subsidiary of a Tokyo company, J Power, to build the structures that would house the turbines and hook them up to the power lines, then operate the plants for 10 years. Only then would they revert to city ownership.

So already San Francisco is waffling on the public power issue. (Why, for example, can't the city build the facilities itself and hire its own engineers to hook up the turbines and run them? Why do we even need a private, outside partner?)

Then there's the environmental impact. In theory, if the peakers only ran a few hours a day, they would spew less junk into the air than the Mirant plant currently does. And Cal-ISO ...