BESS Project Finance Model (tolling then merchant, degradation and augmentation, DSCR-sculpted debt)

A single-asset battery energy storage (BESS) project finance model with the two things a solar or wind model cannot give you: a revenue stack that switches from a tolling contract to merchant income, and a battery that fades and gets augmented. Up to 30 operating years, DSCR-sculpted debt with a gearing cap, project and equity returns, nothing hidden.

• Inputs sheet: power (MW) and duration (hours), round-trip efficiency, cycles per day, availability, annual capacity degradation, augmentation year and cost per MWh restored, operating life, capex per MWh of energy capacity plus grid, land and development, financing fees, tolling fee per MW-year with term and escalation, merchant net arbitrage margin per MWh discharged, capacity payment and ancillary services per MW-year with inflation, O&M per MWh of capacity and fixed costs with escalation, target DSCR, maximum gearing, interest rate, tenor, tax rate, depreciation period, discount rates, and three scenario multipliers (price, capex, throughput).

• Operations sheet: usable energy as a share of nameplate (fade, reset at augmentation), energy discharged, tolling flag, tolling revenue, merchant arbitrage revenue, capacity and ancillary revenue, total revenue, opex, augmentation cost in its year, EBITDA, depreciation, unlevered tax, CFADS for sizing and the unlevered project cash flow, for every year.

• Debt sheet: service sculpted to the target DSCR, debt capacity as the present value of that service, the gearing cap, pro rata scaling when the cap binds, the full schedule (opening, interest, service, principal, closing), actual tax with the interest deduction, equity cash flow, DSCR achieved each year, minimum and average DSCR, LLCR, and a check that the balance reaches zero at the end of the tenor.

• Returns sheet: unlevered and levered cash flows, project IRR and NPV, equity IRR and NPV, payback year, DSCRs, year 1 revenue, EBITDA and energy discharged, capex per kWh.

Design choices are written on the Guide sheet: augmentation is priced on the energy actually restored and expensed in its year (so it reduces CFADS and tax that year); the merchant margin is entered net of charging cost and round-trip losses; debt sizing uses unlevered tax to avoid a circular reference; construction is a single point at year 0, one tranche, no DSRA or cash sweep. Every default is an example value, not market data, and the Inputs sheet says so. The model was rebuilt independently in Python and matched cell by cell (capex, debt capacity, DSCRs, both IRRs, the augmentation year, the first merchant year) before listing. Live formulas, no macros, no locked cells. Excel and Google Sheets.

Who it is for: developers and investors sizing debt against a tolling agreement, teams testing what merchant tail a lender will give credit for, students learning why storage models need a fade and augmentation line. Pairs with the Bindler solar and onshore wind models, which share the structure.