At 0630 GMT, the rand traded at 17.6925 against the dollar, around 0.4% weaker than its previous close.
The dollar was up over 0.3% against a basket of currencies, as investors braced for a large interest rate hike from the U.S. Federal Reserve this week.
Eskom on Sunday implemented "Stage 6" power cuts, a level only seen twice before, which means at least six hours without power daily for most South Africans.
The company has struggled to keep the lights on in Africa's most industrialised economy for more than a decade, choking economic growth and fuelling public frustration.
The government's benchmark 2030 bond was modestly weaker in early deals, with the yield rising 2.5 basis points to 10.365%.
(Reporting by Alexander Winning; Editing by Toby Chopra)
