FCAS vs. arbitrage: How batteries earn in Australia's NEM

Australia has one of the most active and well-documented battery storage markets in the world. It has the data, the scale, and the track record to show what utility-scale battery energy storage systems (BESS) actually earn, and where the revenue comes from.

In Q1 2026, grid-scale batteries across Australia's National Electricity Market (NEM) earned AUD 96.9 million, more than double the AUD 44 million recorded in the same quarter a year earlier. Arbitrage accounted for 97% of that revenue, with FCAS contributing just 3%, down 43% year on year.

Global BESS additions are on track to exceed 450 GWh in 2026, with the market projected to reach USD 105.96 billion by 2029. Oceania, led by Australia's National Electricity Market (NEM), is at the forefront of that growth. For project teams designing BESS assets in this region, the revenue question is not abstract. It directly influences how a project is sized, how long it runs, how its dispatch logic is configured, and how it is modeled for financing.

The two primary ways storage earns in the market are frequency control ancillary services (FCAS) and energy arbitrage. Understanding how each works and where each is heading is the starting point for building a successful project.

What is FCAS, and how does it work?

The term FCAS is specific to Australia's NEM. The underlying mechanism, fast-acting resources correcting grid frequency imbalances, exists in every power market. Europe calls it frequency containment reserve (FCR). The United States uses frequency response or regulation. In each case, the goal is the same: when supply and demand fall out of balance, something needs to pull frequency back before the deviation becomes a problem.

Within the NEM, FCAS is divided into two categories:

1) Regulation services run continuously. The Australian Energy Market Operator (AEMO) sends automatic signals to batteries and other resources every few seconds, adjusting their outputs to keep the frequency stable during normal demand fluctuations.

2) Contingency services are reserves held for major disruptions, such as a large generator tripping or a transmission line failing. In the NEM, contingency FCAS is divided into four time bands:

• Very Fast (1 second)

• Fast (6 seconds)

• Slow (60 seconds)

• Delayed (5 minutes)

Each has a raise and lower function depending on whether the grid needs power injected or absorbed.

Batteries suit this role well. A BESS can switch from charge to discharge in milliseconds, far faster than gas turbines or hydro units, whose response times are measured in seconds to minutes. In Australia's NEM, that speed advantage has made batteries the dominant providers of very fast frequency response.

How does FCAS earn revenue in Australia?

AEMO replaced the old Causer Pays system with Frequency Performance Payments for regulation services, which track each asset's real-time impact on frequency. The old system recovered the cost of frequency regulation from those who caused deviations. The new system goes further, directly rewarding assets that correct them based on real-time performance, and penalizing those that make things worse.

For contingency FCAS, cost responsibility follows risk exposure. If frequency needs to be raised, generators and batteries pay for the service. If it needs to be lowered, retailers and large energy users carry the cost. Whoever is most likely to create a frequency problem pays for the response that solves it.

New Zealand operates its own frequency keeping and instantaneous reserve markets under the Electricity Authority, with a different structure but the same function. In Pacific island networks, where grid stability is harder to maintain and diesel backup is expensive, battery-based frequency response is drawing growing interest as an alternative.

Has FCAS reached its earnings ceiling in Oceania?

In Australia, all the recent data points to yes. According to Modo Energy, contingency FCAS revenues have declined year on year since 2020, reaching their lowest point in 2025, driven by increases in battery capacity competing for a market with a fixed ceiling. Once enough batteries are available to meet the grid's frequency response requirement, additional supply simply pushes prices down.

Australia reached that saturation point earlier than most expected. The same has happened in Great Britain and Sweden. It is a structural feature of frequency response markets: they are finite, and batteries fill them fast.

For project teams, this has a direct implication. FCAS can contribute meaningfully to cash flow in the early years of operation. It should, however, not anchor long-term project economics. That role belongs to arbitrage.

What is energy arbitrage?

Energy arbitrage extracts value from wholesale electricity price volatility. A BESS operator charges when prices are low, typically during off-peak periods or when renewable generation floods the grid, and discharges when prices are high. The profit is the spread between charge and discharge prices, after accounting for round-trip losses and operating costs.

As variable renewables supply a larger share of the grid, the conditions for arbitrage become more reliable, not less. Solar generation peaks at midday, driving wholesale prices down. Evening demand surges, and prices spike. That daily cycle creates a recurring window that utility-scale BESS is well positioned to capture, and it grows wider as solar penetration increases.

South Australia and Queensland have consistently recorded the NEM's most acute price volatility. In South Australia, the combination of high renewable penetration and reliance on a small number of interconnectors means prices can swing sharply when supply and demand fall out of alignment. According to AEMO's South Australian Electricity Report, price volatility in the state rose 168% in 2024-25, driven by tight supply conditions and interconnector constraints.

In Q1 2026, a single weather event pushed South Australian prices to $19,000/MWh across 28 dispatch intervals in one evening. For BESS operators, these conditions create recurring arbitrage opportunities that more uniformly connected regions cannot match. These are strong arbitrage markets. Project teams designing for these regions have more to work with than most.

How do BESS arbitrage strategies work in practice?

Time-of-use optimization is the most straightforward approach: charge during overnight or midday solar troughs, discharge during evening peaks. It works best where demand patterns are predictable and price spreads are consistent.

Day-ahead market participation adds a forecast layer. Operators bid capacity into low-cost windows based on price projections and schedule discharge around expected peak periods.

Real-time arbitrage is the most demanding approach. Prices in volatile markets can move dramatically within an hour. Operators with responsive control systems can act on those movements in near real-time, capturing value that a fixed schedule would miss. In markets like the NEM, where price spikes can reach thousands of dollars per megawatt-hour in a matter of minutes, the control system is not a secondary consideration. It is a core part of the revenue model.

Across all three approaches, operators earn more when they manage charge and discharge decisions dynamically rather than following a fixed schedule. Batteries that respond to evolving price signals outperform those that don't.

Arbitrage is leading, and the NEM data confirms it

Abritrage’s share of total battery revenue across Australia's NEM has grown steadily as FCAS prices have fallen, and the conditions driving it, rising solar penetration, tighter grid constraints, and more volatile prices, are not reversing.

In the U.S., 41% of utility-scale batteries name arbitrage as their primary use case, with 66% including it as part of their broader revenue mix. That ratio has held steady even as deployment scales, suggesting arbitrage is a durable model rather than an early-stage phenomenon.

Some projects are opening up to more than one revenue stream from the start. Hornsdale Power Reserve  demonstrated this from the outset: its capacity was structured from day one across both grid services and energy arbitrage, and its operating history across both markets helped establish the commercial case for multi-revenue BESS projects in Australia. Newer, longer-duration batteries are now extending that model further, with assets like Bouldercombe in Queensland earning strong returns across both FCAS contingency and arbitrage in 2024.

Revenue strategy starts at the design stage

Whether you are developing a standalone BESS project or a hybrid solar-plus-storage asset in Australia's NEM, the complexity of the design process is one of the biggest barriers to moving quickly. RatedPower is built to remove that barrier.

The platform enables engineers and developers to run detailed feasibility studies and technical designs for utility-scale BESS and hybrid projects faster than traditional methods allow. From site layout and equipment configuration to yield analysis and export reports, RatedPower gives teams the data they need to make confident decisions at every stage of the development process.

For developers building an arbitrage strategy in the NEM, RatedPower's dispatch modeling is particularly valuable. The platform simulates how a battery asset will charge and discharge across different market scenarios, helping teams understand potential revenue under varying price spread conditions before committing capital. 

That visibility matters in a market like Australia's, where intraday price spreads in regions like South Australia and Queensland can shift dramatically depending on solar penetration, interconnector availability, and seasonal demand patterns. Getting the operational profile right before the project is built is not a refinement. It is a core part of the investment case.

RatedPower also supports the growing diversity of BESS project types in the NEM through its Integrate Generation Profile feature. Rather than limiting simulation to internally modeled solar generation, this capability allows users to upload real or contractual generation data from wind, hydro, or hybrid sources to simulate standalone BESS dispatch. 

Teams can define flexible simulation horizons with built-in degradation and end-of-life logic, providing a more accurate picture of long-term asset performance over a 20-year operating life. The feature preserves RatedPower's trusted AC-BESS dispatch, financial logic, and key performance indicators (KPIs), while adding greater flexibility in configuring charging sources and energy delivery limits.

For developers navigating a market where the pipeline is growing fast and speed to financial close increasingly determines which projects get built, having a reliable, automated design workflow is not a nice-to-have. It is a competitive advantage.

If you are planning BESS or hybrid solar-storage projects in Australia or across Oceania, explore how RatedPower can help your pipeline. Request a live demo here.

Design for the market you will be operating in

Australia and broader Oceania offer one of the most data-rich environments for understanding what battery storage actually earns. The lesson is clear: FCAS provides a useful early revenue foundation, but arbitrage is where long-term value accumulates.

For project teams in this region, the question is not which revenue stream to prioritize in isolation. It is about designing a project capable of accessing both, calibrated to the market conditions it will face over decades of operation. That work starts at the design stage.

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