The production decline and weaker metal prices will see Impala's headline earnings per share (HEPS) decline by more than 20%, compared to the 38.53 rand ($2.07) reported last year.
Impala said in a production update its refined PGM output for the year was 2.96 million ounces, just missing out on its production guidance range between 3 and 3.15 million ounces.
"Regional power constraints provided a notable impediment to operational continuity and delivery," Impala said.
Production of about 101,000 ounces of PGMs was deferred as a result of frequent power cuts and the resulting delay in restarting a refurbished furnace in the April-June quarter, Impala said.
Power cuts had also impacted Impala's operations in Zimbabwe, where its operations include the 87% owned Zimplats and Mimosa, an equally owned joint venture with Sibanye Stillwater.
Impala, which has recently taken control of mid-tier producer Royal Bafokeng Platinum's shallow, high quality assets, will release its annual financial results on Aug.31.
($1 = 18.6352 rand)
(Reporting by Nelson Banya; Editing by Bernadette Baum)