PJM will require all steam generators to adjust their capacity ratings based on summer peak load conditions under manual changes outlined to the Planning and Market Implementation committees last week.

Manual 21 currently requires such temperature corrections only for combustion turbines and combined cycle units. The revisions will extend the requirement to coal and nuclear steam units.

About 60% of steam units already perform temperature corrections, with half increasing their capacity ratings and half reducing them, said PJM’s Tom Falin. The average adjustments were 0.5% with the largest adjustment 2%.

PJM also will begin requiring hydropower and pump storage units to perform their annual capacity tests — now allowed to be conducted any time — during the summer.

The adjustments can affect generators’ installed capacity values as well as capacity interconnection rights.

PJM plans to implement the changes after seeking endorsement by the Markets and Reliability Committee in the first quarter of 2014.

The changes will be incorporated in PJM’s planning studies in summer 2014, with a likely transition period before use for markets purposes.