A central forecast is closer to an architect’s drawing than a completed building. It describes what may happen under a set of assumptions. It does not guarantee the timing, volatility or availability of cash needed to service debt.
At a glance
- Median merchant revenue should not be treated as contracted project cashflow.
- Longer duration can sacrifice some central-case return while buying resilience to service saturation and forecast error.
- Revenue streams cannot be assessed independently when the same MW, state of charge and cycling budget support all services.
- Known bad rules can often be priced; undefined future rules can prevent credible debt sizing altogether.
Duration can be insurance against being wrong
Forecast-to-financeability bridge
Market forecastPrices and services
→
Joint dispatchSOC and service conflict
→
Net cashflowFees, losses and degradation
→
Downside caseSaturation, delay and rules
→
Debt capacityHaircut and DSCR
The forecast is only the first input. Debt capacity appears after physical dispatch and lender downside tests.
Harmony Energy’s experience with two-hour batteries provides a useful way to think about duration. A shorter-duration asset may appear superior while high-value ancillary services are deep and unsaturated. If those services compress earlier than expected, the asset can lose both revenue and strategic flexibility.
Additional duration may lower the central-case IRR while expanding the set of markets the battery can enter and reducing dependence on one service. The investment decision should therefore compare more than the expected return. It should test capital survival under service saturation, spread compression and dispatch error.
Battery duration is not only additional MWh. It can be an insurance premium against getting the future market structure wrong.
Revenue stacks share one physical battery
Arbitrage, FCAS, capacity and balancing are often presented as separate columns. In operation, the battery buys and sells across markets while constrained by the same state of charge, availability, efficiency, degradation and connection capacity. Charging may appear as negative revenue in one market before enabling a profitable discharge elsewhere.
A financeable model therefore needs a single physical ledger:
- interval charge and discharge volumes and prices;
- state of charge, efficiency, availability and degradation;
- net settlement across all markets;
- optimiser fees, imbalance and redispatch outcomes;
- conflicts where the same capacity cannot perform two services simultaneously.
The relevant metric is the net contribution per cycle and per MW, not a label assigning each electron to a revenue stream.
Uncertainty can remove debt capacity
An explicit but unfavourable network charge can be modelled, haircut and priced. A material charging rule that remains undefined after 2029 is harder: it may prevent lenders from forming a credible downside case. The same logic applies to connection constraints, marginal loss factors and market redesign.
A generic ±10% regulatory sensitivity is not enough when a rule change can alter whether the asset may participate, when it can energise or which network charges it must carry.
A three-layer BESS finance model
- Debt foundation: repeatable or contracted revenue with transparent lender haircuts.
- Operating scenarios: service saturation, spread compression, availability, degradation, delay and optimiser underperformance.
- Equity optionality: upside from volatility, new services and rule changes without relying on it to support DSCR.
COD delay should also flow through equipment repricing, contract commencement, interest during construction and the revenue curve. Simply shifting revenue one year to the right understates the damage.
Pre-DD implication: F3 establishes the dispatch boundary and physical constraints. F4 separates forecast upside from cashflow that can support debt. The key question is not whether the central case makes money, but which wrong assumption can make the project fail and what design, contract or capital structure absorbs it.
Source · external signal, independent applicationBased on Modo Energy’s The Transmission interview with Paul Mason of Harmony Energy. Market observations are contextual signals, not forecasts for Australia. Financeability application is independent analysis. Commentary only — not financial product or investment advice.
Basis
Written from public information and Heliovulcan’s own screening work. Where an external source informs the argument, it is named in the text rather than absorbed into it.
Status
Analytical note on project logic at screening grade. Not legal, financial, tax, engineering, investment or formal due-diligence advice, and not a financial product recommendation. Any figure should be independently verified before a commercial decision.
