Most commercial real estate deals in America get underwritten in Excel. That is not an accident and it is not a mistake. Excel is flexible enough to model anything, everyone in the industry can read it, and a good operator with a good template can get to a number. If you are evaluating PropCalc™ against the spreadsheet you already have, you deserve a comparison that starts from that honest baseline rather than pretending Excel is incapable.
So here is where Excel genuinely wins. Total flexibility: if your deal has a structure nobody has seen before, a spreadsheet will bend to it. Universal literacy: your lender, your partner, and your attorney can all open the file. Zero marginal cost if you already live in it. For a one-off structure that no product anticipates, the spreadsheet is still the right instrument.
Now the other side, and it has less to do with capability than with integrity under pressure. Audits of complex spreadsheets consistently find errors in a large share of them, and underwriting models are complex spreadsheets. A pasted row that breaks a formula range. A hardcoded cell someone typed during a call and forgot. A circular reference patched with a manual value. None of these announce themselves. The model still produces a number, and the number is wrong quietly.
The second failure mode is key-person fragility. A serious Excel model is usually legible to exactly one person, its builder. When a partner asks why year six cash flow dips, the answer lives in a nest of tabs only the author can navigate. When that author is you, every deal routes through your hours. That is a bottleneck problem before it is an accuracy problem.
The third is depth versus time. Excel can model per-tenant renewal probability, downtime, individual escalation structures, and a full waterfall. Very few operators actually build that, because building it takes hours per deal and breaks the moment the rent roll changes shape. So the working compromise becomes blanket vacancy, one rent growth number, one renewal assumption. The spreadsheet is capable of depth; the deadline is not.
A purpose-built underwriting simulator changes the terms of that compromise. In PropCalc, per-tenant assumptions are not formulas you construct, they are first-class inputs that already exist for every lease. The capital stack, the waterfall, and the stress grid are already wired to the rent roll, so changing one assumption recalculates everything downstream without anyone maintaining the plumbing. The depth that took hours in a spreadsheet takes the same time as the shallow version, which removes the reason the shallow version existed.
The honest decision framework: if you underwrite a few deals a year and enjoy maintaining a model, a disciplined spreadsheet can serve you. If deal flow is real, if partners and lenders read your output, and if you have ever been unable to explain your own number under questioning, the spreadsheet is costing more than it appears to.
One last point, because this is not actually either-or. PropCalc exports a full institutional Excel workbook of any deal. The simulator does the modeling; the spreadsheet remains the lingua franca for whoever needs it. You are not choosing against Excel. You are choosing what builds the numbers that go into it.