A solar tariff calculator with integrated financial statements and a cash waterfall — an institutional-grade tool for assessing a proposal to build and operate a solar PV farm or rooftop project, built in Excel.

Most financial models start with a price and tell you what return it produces. This one runs the other way. You specify the Equity IRR your investors require, and an automated mechanism back-calculates the tariff needed to deliver it. That inversion changes the conversation entirely — instead of guessing at a price and hoping the returns work, you start from the return you must achieve and find out exactly what you need to charge.

For anyone bidding into a solar auction, negotiating a PPA or setting a price for a concession, that is the question that actually matters. This solar tariff calculator answers it directly, deriving the required price from your desired Equity IRR, operational capacity and expected cost inputs.

Around that engine sits a complete project finance structure — Project and Equity IRR and NPV, DSCR, LCOE, equity payback, a full cash waterfall and integrated three-statement financials — so the tariff it produces is grounded in a properly built model rather than a standalone calculation.

How the Tariff Calculation Works

Revenue is derived, not assumed. The solar tariff calculator takes your target Equity IRR and operational capacity and works backwards through the cash flows — after debt service, after tax, after operating cost — to establish the price per unit that leaves shareholders with exactly the return they asked for. A VBA routine handles the iteration.

Cost is split into two parts, as project finance requires. Construction cost is spread proportionately across the construction period, feeding the funding requirement along with interest and fees incurred during the build. Operating cost then takes over once the plant is live, split between fixed cost, variable cost and general and administrative expense as a fixed annual charge.

Tariff and LCOE Together

The model produces both the required tariff and the Levelised Cost of Energy, and the relationship between them is the entire commercial picture. LCOE tells you what the electricity costs you to produce across the asset’s life. The tariff tells you what you need to charge to earn your target return on top of that.

Seeing both side by side shows you the margin you are asking for, and whether it will survive contact with a competitive auction. If your calculated tariff sits well above prevailing market clearing prices, the model tells you so before you submit a bid rather than after.

Debt Structured Two Ways

Funding requirement is calculated from total construction cost plus interest and fees during construction, then funded in a debt-equity ratio you define. Repayment runs on either an annuity profile — equated payments across the life of the loan — or a sculpted profile, where repayment follows the cash flow available at a defined Debt Service Coverage Ratio. Sculpting is what most project finance lenders actually use, and switching between the two shows immediately how much the repayment structure alone affects the tariff you must charge.

A 70-Year Horizon

The model runs on a flexible annual timeline and can forecast up to seventy years across both construction and operations. That is far beyond what most templates offer, and it matters for solar assets whose economic life routinely runs well past the standard twenty-five year modelling convention.

A short horizon forces the tariff up, because capital has less time to be recovered. Being able to model the genuine asset life often makes the difference between a bid that wins and one that prices itself out.

What the Model Produces

• Required Tariff — back-calculated from your target Equity IRR and capacity
• Project & Equity IRR and NPV — returns to the project and to shareholders
• Levelised Cost of Energy (LCOE) — cost per unit across the asset’s life
• DSCR — the debt service coverage lenders scrutinise first
• Equity Payback Period — time to recover shareholder investment
• Cash Waterfall — the full cascade of cash through the structure
• Integrated Financial Statements — income statement, balance sheet and cash flow, fully linked
• Sensitivity Analysis & Optimiser — test how the tariff responds across key variables

Who This Solar Tariff Calculator Is For

• Solar developers pricing a proposal to build and operate a farm or rooftop project
• Bidders in solar auctions and PPA processes establishing a defensible price floor
• Procuring authorities and regulators testing whether a submitted tariff is reasonable
• Renewable investors checking what return a given tariff actually supports
• Project finance advisors preparing bid models and negotiating power purchase agreements

Why This Model

New to these metrics? Read an overview of the internal rate of return. For a model built to your own specification, see our project finance advisory services, or browse the full range of PPP and project finance templates.