The Fixed Charge Trap: Surviving the ERTSA Tariff Unbundling

The Market Anchor

Last week, the National Energy Regulator of South Africa (NERSA) officially gazetted the Eskom Retail Tariff Structural Adjustment (ERTSA) consultation document for the 2026/27 financial year.

The mainstream press focused almost exclusively on the single digit volumetric price increase. The forensic financial reality buried in the structural unbundling is an absolute disaster for private infrastructure. NERSA just authorized a targeted regulatory strike against private solar savings.

The new ERTSA framework aggressively shifts utility revenue recovery away from volumetric per-unit energy charges and piles it onto fixed monthly capacity fees.

For years, heavy industrial and commercial off-takers installed grid-tied rooftop solar to slash their energy consumption, legally depriving the utility of volumetric revenue. The ERTSA unbundling is the utility's counterattack. Under the new structure, even if an off-taker self-generates 100 percent of their midday power, they are still forced to pay a massive, unavoidable fixed charge simply for being physically connected to the grid.

The Multidisciplinary Blast Radius

A 15-year corporate Power Purchase Agreement relies entirely on the mathematical spread between the private generation tariff and the utility retail tariff. When the utility fundamentally changes the structure of its bill, the arbitrage equation violently collapses.

• The C&I Off-Taker Risk: You signed a 15-year PPA to lower your operational expenses. But because the ERTSA structure introduces heavy fixed capacity charges, your total blended energy cost suddenly spikes. You are paying the private developer for the solar power, and you are still paying the utility massive fixed fees for the grid connection. The modeled savings evaporate.
• The Developer Risk: If your financial models rely on "energy-only" savings calculations, your pipeline is mathematically obsolete. You can no longer pitch a PPA based on the assumption that saving a kilowatt-hour automatically saves the off-taker money.
• The Lender Risk: If the off-taker projected savings disappear due to fixed tariff inflation, the off-taker will aggressively dispute the private PPA or attempt to legally force a renegotiation. A debt facility built on volumetric arbitrage is mathematically exposed to regulatory shock.