The story
Why Rufineer exists
The logic of a project finance deal is simple to say. Sell this much energy at this tariff. Repay the loan from what is left. Keep six months of debt service in reserve. In Excel it becomes thousands of cells copied across hundreds of columns, and one wrong reference can sit unnoticed through a whole transaction.
Rufineer's founder builds and reviews these models for energy and infrastructure deals in Southern Africa. Rufineer is the answer: write the logic once, in lines a colleague can read, and let a compiler do the part people get wrong. It lays out the workbook, converts the units, and checks every loop and every balance.
The output is still Excel. Lenders, auditors and model reviewers work in Excel, and Rufineer respects that. Every workbook it writes follows the FAST Standard, keeps every number on the Inputs sheet and never switches on iterative calculation. What changes is where the model lives: in plain text, under version control, with every change reviewable.
Rufineer's design comes from reading real workbooks. We read 698 project finance models, course exercises and lender models for what they build and the mistakes that slip through, and mapped a second library of 741, across twelve sectors, family by family against the language (Coverage shows what it can express today and what is planned). That is design research, not a certificate that any model is right.
What is tested, automatically and on every change, is Rufineer itself: every step of every tutorial is replayed and its results compared, every example that compiles is opened in a spreadsheet and must come out solved, and the compiler is held to the reference compilers that came before it, formula for formula. A model that passes all its checks is internally consistent; whether its assumptions and logic fit the deal is still a modeller's review, which the audit panel makes faster.