NERSA's ERTSA 2027–28 tariff consultation — triggered by a 4 September 2026 invitation to comment — is the forward-pricing wildcard every C&I solar and BESS buyer must stress-test before signing any PPA or wheeling agreement, as Eskom's fixed-cost glide path hits 100% and gen-wheeling credit rates are structurally adjusted from April 2027.

Why the ERTSA 2027–28 Consultation Is the Most Important Regulatory Event in C&I Solar Right Now

On 4 September 2026, NERSA published its consultation paper inviting public comment on Eskom's proposed tariff structure for the 2027/28 financial year — an event that most C&I energy buyers either missed or treated as routine regulatory housekeeping. That would be a costly mistake. NERSA published the consultation paper to finalise Eskom's approved 8.83% tariff increase and adjustments to fixed charges for the 2027/28 financial year. But the headline percentage is the least important number in the document. What matters for every commercial and industrial solar and BESS buyer in South Africa are the structural mechanics beneath that number — mechanics that will directly reprice every PPA, wheeling agreement, and behind-the-meter business case signed between now and April 2027.

The Glide Path Reaches Its Destination: Fixed Costs Hit 100%

The single most consequential structural change embedded in the 2027/28 ERTSA is the completion of Eskom's three-year fixed-cost unbundling glide path. Eskom has been implementing these fixed fees over a three-year glide path. Currently, they are at 66.6% of the final amount Eskom wants to charge. Next year, they will increase to 100%.

To understand what this means in practice, recall the mechanics: the fixed portion of the Generation Capacity Charge (GCC) is increased from 20% in FY2026 to 30% in FY2027, with the remaining 70% included and recovered through the energy charge. For FY2027/28, the intention is to move the remaining energy-embedded portion of fixed costs into explicit standing charges, completing the unbundling. The ERTSA aims to raise Eskom's fixed fees to 100% of the final amount. A separate service and administration charge will also jump by almost 50%.

For C&I solar developers and their clients, this is a paradigm shift in displacement economics. Behind-the-meter solar has historically displaced kWh, with every unit self-generated reducing the variable energy charge. As fixed charges move to 100%, a greater fraction of the Eskom bill becomes inescapable regardless of how much self-generation a site deploys. A business that installed rooftop solar in 2023 or 2024 to reduce its kWh consumption from Eskom has cut its energy bill — but its grid connection size has not changed. The GCC is levied on that connection capacity. As the GCC steps up, the saving from energy displacement is being partially clawed back through the fixed charge side of the bill.

The tariff impact on direct consumer categories is stark. Under the proposed 2027/28 structure, Homepower/Homeflex 1 fixed daily charges rise by 20.1% (from R23.02 to R27.65 per day), Homepower/Homeflex 2 by 14.9% (from R42.68 to R49.05), Homepower/Homeflex 3 by 11.9% (from R84.33 to R94.38, totalling R2,871 per month), and Homepower/Homeflex 4 by 23.3% (from R17.86 to R22.03 per day). The tariff charges are scheduled to come into effect on 1 April 2027.

The R54.7 Billion Error Loading Into April 2027 Tariffs

Behind the 8.83% headline lies a regulatory asset base correction that is quietly loading a massive additional cost burden onto 2027/28 tariffs. NERSA has approved Eskom's additional allowable revenue of R54.734 billion following a re-determination of the utility's Generation Regulatory Asset Base for the 2025/26, 2026/27 and 2027/28 financial years, correcting a data input error of approximately R54 billion linked to depreciation calculations and the valuation of Eskom's generation assets.

The recovery schedule is not evenly spread. Eskom will recover R12 billion in the 2026/27 financial year and R23.013 billion in 2027/28. That means the single largest chunk of the error correction lands precisely in the tariff year that kicks in from April 2027. For 2027/28, the original MYPD6 approval was 6.19%. The R23 billion slice adds 2.64 percentage points. Result: 8.83%. And critically, the deferred R19.7 billion lands on the period after that — meaning structural tariff pressure does not ease after 2027/28.

For PPA and wheeling agreement signatories, this has one practical implication: the 8.83% is not a high-water mark. It is an artificially compressed figure that absorbs only part of the regulatory error, with a further tranche still pending allocation into the next MYPD period.

Gen-Wheeling Credit Rate Adjustments: The Delivered PPA Floor Is Moving

NERSA's structural changes to the Gen-Wheeling tariff category add another layer of complexity for C&I buyers purchasing power through third-party wheeling agreements. The portion of the GCC included in the energy charge is excluded from the energy credit provided under wheeling and net-billing (offset) transactions — a structural change that has been in force since FY2027 and which reduces the effective wheeling credit that off-takers can claim against their Eskom bill.

Furthermore, NERSA has approved the removal of affordability subsidy credits from wheeling transactions. The Energy Regulator approved removing the affordability subsidy credit for customers wheeling energy so that all customers contribute fairly to inter-tariff subsidies. The impact will largely be felt by private consumers supplied by private generators and/or private traders wheeling power across the transmission and distribution networks, who will now contribute to the subsidy instituted in the electricity supply industry.

The net effect: the delivered cost floor of a wheeled PPA has risen structurally. The wheeling credit rate tariff based on the NSP's avoided cost must be justified and approved by NERSA. Full tariff charges are raised for all the energy supplied through the meter, for both the NSP-sold energy and the wheeled energy, including all approved fixed charges, and contributions to surpluses and subsidies. The amount of wheeled energy is then credited as a separate transaction on the customer bill using the wheeled energy kWh allocated to the off-taker's electricity bill, multiplied by a Wheeling Credit Rate Tariff. As fixed charges rise to 100% and the subsidy credit is stripped from wheeling transactions, the net credit rate narrows — and the all-in delivered tariff from a wheeled solar PPA must be modelled against a higher residual Eskom charge base.

What NERSA Is Actually Consulting On — And What It Cannot Change

It is critical that C&I buyers understand the scope — and limits — of this consultation. NERSA's Executive Manager for Electricity, Rhulani Mathebula, clarified that the consultation does not revisit the total revenue amount determined in 2025. The quantum of money Eskom will collect is already locked. The underlying revenue determination is already done, and what is at stake is who pays how much, through which tariff components.

This means the ERTSA consultation is a tariff structure exercise, not a tariff level exercise. For C&I developers, the consultation window — which closed 2 October 2026 — was the last opportunity to formally influence how fixed versus variable charges are apportioned across commercial tariff categories, and how gen-wheeling credit rates are calibrated for the coming financial year. The regulator said input from interested and affected parties could influence the final decision.

NERSA is expected to issue its determination ahead of the April 2027 implementation date. The window between now and April 2027 is the stress-test period for every deal currently in pipeline.

BESS Dispatch Optimisation in Q1 2027: The Structural Arbitrage Is Getting Wider

The convergence of rising fixed charges and an 8.83% blended tariff increase creates a paradoxical opportunity for BESS: as the variable (kWh) component of Eskom tariffs is partially compressed to fund the fixed cost rebalancing, time-of-use differentials in the energy charge may narrow slightly — but the absolute Rand value of peak tariff slots continues to escalate. BESS systems optimised against Megaflex or Miniflex TOU windows remain among the strongest investment cases in South Africa's commercial energy market.

For C&I sites already deploying solar, BESS dispatch optimisation in Q1 2027 must account for the new tariff structure from day one of April 2027. Any BESS dispatch algorithm calibrated on the current 30% fixed GCC structure will be mispriced on 1 April 2027 when the full 100% fixed-cost unbundling kicks in. Developers and energy managers need to model revised avoided-cost curves now, not after the NERSA determination lands.

The Three Stress-Tests Every C&I Buyer Must Run Before Signing

C&I finance teams should model the full three-year trajectory. With an 8.83% increase confirmed for FY2028 and additional NERSA revenue recovery still to be loaded, a PPA or solar lease signed today locks in a fixed or CPI-linked energy rate against a grid tariff that is structurally escalating above inflation. The longer the tenure, the stronger the hedge value.

Specifically, every C&I buyer should stress-test three scenarios before executing any PPA or wheeling agreement:

Stress Test 1 — Fixed-Cost Floor Shift: Model the site's all-in Eskom bill under 100% fixed-cost recovery from April 2027. Calculate the true displacement value of solar kWh against a bill that now has a larger inescapable fixed component. Rooftop solar economics remain strong, but IRR projections based on the FY2027 tariff structure will overstate savings by between 8–15% if not updated for the FY2028 fixed-charge step-up.
Stress Test 2 — Wheeling Credit Rate Erosion: For off-site wheeling deals, rebuild the delivered PPA cost model with the reduced gen-wheeling credit rate (affordability subsidy removed, GCC embedded portion excluded). Any PPA pricing negotiated before the April 2026 tariff changes should be treated as a different base case.
Stress Test 3 — Tail Risk Beyond 2027/28: The deferred R19.7 billion lands on the period after 2027/28. Any PPA or wheeling agreement extending into FY2029 and beyond must price in at least one further above-inflation escalation event driven by this unrecovered regulatory error tranche. Long-tenor agreements (10–20 years) that are CPI-linked will likely still outperform grid tariffs — but the margin of outperformance must be verified under a rising-fixed-charge scenario.

The SolarXgen Field Intelligence View

From our project pipeline across KwaZulu-Natal, Gauteng, and the Western Cape, we are seeing a clear pattern: C&I buyers who modelled their PPA economics on the 2025/26 tariff structure are now facing revised financial models that change project approval timelines. The ERTSA 2027–28 consultation is not an abstract regulatory event — it is a direct input into the financial model of every deal currently in due diligence.

While the headline 8.83% figure follows closely on the heels of the 8.76% hike implemented in April 2026, energy analysts and civil society bodies warn that the actual financial hit for businesses will be far more severe due to aggressive restructuring of fixed daily service fees. The C&I solar and BESS case has never been stronger in absolute terms. But the case must be made with the right numbers — and those numbers change on 1 April 2027.

Do not sign a PPA or wheeling agreement based on yesterday's tariff model. The ERTSA 2027–28 determination is the forward-pricing wildcard that belongs in every deal's sensitivity table before execution.