Comparison
Power BI vs. spreadsheets for agency reporting.
Spreadsheets aren't the wrong tool because they're old. They're the wrong tool past a certain scale because they have no shared definition layer, so every copy is free to drift. Here's where that actually shows up.
| Dimension | Spreadsheets | Power BI (with a semantic model) |
|---|---|---|
| Where a metric's definition lives | In whoever built the tab's head, or scattered across cell comments and tribal knowledge. | Defined once in a semantic model, documented, and reused by every report that references it. |
| What happens when a definition needs to change | Edited in every copy that used it, if anyone remembers which copies those are. | Changed once, upstream, and every connected report inherits it automatically. |
| Risk of two people reporting different numbers | High. Every copy can drift the moment someone edits a formula under deadline pressure. | Low. Every report queries the same underlying model, so there's one number to disagree about, not several. |
| Adding a new client account | Usually a new spreadsheet, copied from an existing one and manually adjusted. | Usually a new data source added to an existing pattern, using the same report template. |
| Client self-serve access | Rare. Sharing a live spreadsheet with a client is a data-governance risk most agencies avoid. | Practical. Row-level security lets a client see their own account inside a shared report, nothing else. |
| What happens when the builder leaves | The formulas and their logic often leave with them. | The model, its definitions, and its documentation stay with the organization. |
| Time to trace why a number changed | Slow. Usually means opening the file and tracing formulas by hand. | Faster. Certified measures and a documented model make the calculation traceable. |
| Where it still wins | One-off analysis, a quick ad-hoc calculation, or a single account with no reporting cadence yet. | Anything recurring, multi-account, or client-facing, where consistency compounds over time. |
Which is right for you
Both are legitimate, at different scales.
One client, no reporting cadence yet, an occasional ad-hoc question: a spreadsheet is a fine answer. Several client accounts, a recurring monthly report, and more than one person who needs to trust the same number: that's the point where a shared semantic model starts paying for itself. This is the work described on the Data Foundation and Power BI Reporting pages.
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