Electrical generating capacity in the United States could be increased 15 percent without building any new power plants, and the cost of operating the generators could be cut by 60 percent if the newly invented "high-temperature" superconducting materials can be made practical.

These estimates are among the first detailed calculations of the potential economic benefits to be reaped from the copper oxide ceramics that lose all resistance to electrical flow at 321 degrees below zero Fahrenheit. This is the temperature of liquid nitrogen, which is much easier and cheaper to achieve than the 452 degrees below zero required by older superconductors.

There are reports of superconductivity at still warmer temperatures, which would offer even greater economic gains.

The estimates were made by researchers at the Department of Energy's Argonne National Laboratory in collaboration with five other major energy research centers.

The projections assume that the current-carrying capacity of the superconductors can be improved 10 to 100 times and that the materials can be made stronger and more flexible.

The 15 percent increase in generating capacity could be achieved, the study showed, by storing night-generated electricity in superconducting coils that could be tapped during the peak demand hours of midday.

The 60 percent cost savings would come from use of large superconducting AC generators that would lose less electricity to resistance and, therefore, yield more output for a given amount of fuel to turn the generator.

The study also found that costs of local electrical transmission where the wires are normally underground could be cut 40 percent. Even with the savings, it would still be more expensive than transmitting above ground -- the rule for long distances -- because of the high cost of burying the cooling apparatus and insulation.