About the Ancillary Services Revenue
Ancillary services revenue estimation calculates the additional income a grid-connected solar + BESS plant can earn by providing frequency regulation, spinning reserve, reactive power support, or voltage control services to the grid operator — on top of energy arbitrage or PPA revenue.
How to calculate it
- 1Identify the applicable ancillary service market: in India, CERC governs primary frequency response (PFR), secondary frequency regulation (SFR), and reactive power. State-level ancillary markets are being developed under CERC's Ancillary Services Regulations (2022 revision).
- 2Primary frequency response: automatic, no market payment in India currently — required for all large plants above 10 MW as a grid code obligation.
- 3Secondary frequency response (Automatic Generation Control, AGC): BESS can provide AGC by responding to SLDC/RLDC signals. CERC sets compensation rates. Typical AGC capability: ±PCS rated power, with 100 ms response time.
- 4Reactive power: DISCOMs may pay for reactive power injection/absorption. Compensation per kVAR-hour is site-specific.
- 5Estimate annual revenue: ancillary service rate (₹/MW/hour) × available capacity (MW) × participation hours/year.
Worked example
A 5 MW / 20 MWh BESS providing AGC: offered capacity 3 MW (60%), participation 6,000 hours/year, AGC rate ₹1,200/MW/hour. Annual AGC revenue = 3 × 6,000 × 1,200 = ₹2.16 Cr. Stacked with ToU arbitrage (₹1.5 Cr/year): total revenue ₹3.66 Cr/year on a ₹25 Cr BESS investment → 14.6% revenue yield before OPEX.
What you can calculate
- ₹ freq regulation
- Spinning reserve
- RRAS market
- CEA grid code
Frequently asked questions
Can a rooftop solar + BESS system provide ancillary services in India?
Currently, the Indian ancillary services market is open to grid-connected plants of 10 MW or larger. Rooftop and small C&I systems (< 1 MW) cannot directly participate. However, aggregation platforms (virtual power plants) are being piloted — CERC and BEE are working on regulations that would allow aggregated small BESS systems to participate in ancillary markets as a single entity. This is expected to open by 2026–28.
What is the difference between frequency regulation and peak shaving?
Peak shaving is a demand-side service: the BESS discharges during the consumer's own peak demand hours to reduce their maximum demand charge. It is entirely within the consumer's premises and does not require grid operator interaction. Frequency regulation (or AGC) is a grid service: the BESS responds to the grid operator's real-time signal to inject or absorb power, helping maintain system frequency at 50 Hz. Peak shaving value is captured through tariff savings; frequency regulation value is captured through market payments from the grid operator.
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