The utility may struggle to keep the lights on, but its debt is attractive to international investors.
South Africa has sold $2-billion of 12-year bonds in overseas debt markets after boosting the size of the offering.
The rand fell and bond yields rose on Monday morning, as lower commodity prices reflected soft Chinese industrial production figures.
The rand retreated from a tough resistance barrier and languished in a recent range as uncertainty about the ANC election has kept investors jittery.
South Africa is to become the first African government bond market to be included in the World Government Bond Index.
State bonds fell and yields climbed as SA's benchmark stocks booked their biggest daily gain in 16 months, breaking a three-day losing streak.
Transnet and Eskom bonds are now more highly rated than US government bonds, according to the latest ratings by Fitch and Moody's Investments.
The debt crisis in Europe could hit local bonds if it worsens, pushing yields higher than expected as the continent holds 35% of government's debt.
Government bonds have firmed, taking yields on the longer-dated bonds to multi-month lows due to hefty offshore demand.