Execution vs Advice: The Core Difference
- If you want AI to execute the task in your workbook and show you how, Mica does it locally — on your machine, with the file never uploaded — and it is the one here that ships ready to run, with no MCP server to set up.
- If you already have ChatGPT Plus and mainly need formula ideas, ChatGPT for Excel is convenient — and since 2026 it can also apply changes in your workbook, with your approval, in the cloud.
- If you value cell-level citations, Claude explains its logic — and its agent mode can now apply changes in your workbook with confirmation dialogs, in the cloud.
The axis that used to separate these tools — execution versus advice — has narrowed: by 2026 all three cloud tools can execute in your workbook with your approval. What still separates them is where the work runs and where your data goes. A cloud tool executes on its servers and uploads your file; a local tool executes on your machine with the file never leaving it.
Concretely, the same request travels different roads. Ask each tool to sum sales by region: the generators return a formula such as =SUMIFS(sales, region, "West") that you paste and test; the cloud executors can write the SUMIFS into your workbook and run it, but on their servers; a local tool writes it into the right cells on your machine, runs it against your real data, and shows the result — with the file never uploaded.
The second axis is data — and it is now the deciding one. The cloud executors process your workbook on their servers, so the file travels. Mica executes locally, which is the combination that keeps your file on your machine.
ChatGPT for Excel
ChatGPT for Excel is OpenAI's spreadsheet add-in: it writes formulas, analyzes tables, and answers questions about your data in plain language, and it works across Excel and Google Sheets. It runs entirely in the cloud and needs a ChatGPT Plus subscription at $20 a month — a sensible price only if you already hold Plus for other reasons.
On capabilities its natural-language formula writing is a genuine strength, and the Sheets coverage makes it the only one of the trio that reaches a second spreadsheet platform natively.
The capability has changed since 2026: the add-in can now apply changes directly in your workbook — creating or updating live models, modifying cells, formulas, and structure — with your approval before anything changes. The work happens in the cloud, and your spreadsheet content is uploaded to OpenAI's servers to be processed.
For the full picture — availability, what it can and cannot do, and the local alternative — the ChatGPT for Excel guide is the deeper read.
Claude for Excel
Claude for Excel is Anthropic's AI assistant applied to spreadsheet work: it answers with cell-level citations, so every claim is anchored to the specific cells it read to reach the answer. That traceability is a genuine trust advantage — you can check the reasoning against the source before you act on it.
It is strong at explanation, which matters when the question is not "write me a formula" but "why does this number behave this way." The citation trail turns an AI answer into something an analyst can audit, which is rare in this category.
Claude's agent mode goes further than citations: with your confirmation it can update assumptions, build or fill models, edit pivot tables, sort and filter, and write cells directly in your workbook. The work happens in the cloud, and your data is processed on Anthropic's servers. The citation trail still anchors the reasoning — but the execution, when it happens, is not local.
The Claude for Excel guide explains the citation model, real pricing, agent mode, and the local alternative.
Microsoft Copilot for Excel
Microsoft Copilot for Excel is the AI built into Microsoft 365: it suggests formulas, summarizes data, and works with Python in Excel, all inside the environment where your spreadsheets already live. It is priced at about $18–32 per user per month on top of a Microsoft 365 subscription, depending on the plan and billing cycle.
Its native advantage is context. Because it lives where your files and team already are, Copilot needs no add-in install, no separate account, and no switch of platforms for existing M365 users.
Copilot's Agent Mode, generally available since April 2026, takes the product from suggesting to executing: it plans the steps, gets your approval through Plan with Copilot, and then runs multi-step operations in your workbook — modifying formulas, pivot tables, and charts. The execution happens in the cloud, and your data is processed within Microsoft 365.
The Microsoft Copilot for Excel guide covers the plans and Agent Mode in detail.
Full Comparison Table
| Tool | Price | Runs | Executes? | Visibility | Data leaves device? |
|---|---|---|---|---|---|
| Mica | Free download + batteries | Windows desktop, local | Yes — local | Every step shown | No |
| ChatGPT for Excel | Plus $20/mo | Cloud | Yes — in workbook (cloud) | Approval, then applied | Yes |
| Claude for Excel | Pro $17–20/mo | Cloud | Yes — in workbook (cloud) | Confirmation, then applied | Yes |
| Microsoft Copilot | $18–32/mo + M365 | Cloud | Yes — Agent Mode | Plan with Copilot, then runs | Yes |
The three cloud add-ins upload your data to their clouds; Mica keeps your files on your machine — an architectural consequence of executing locally, with nothing for a server to store, train on, or leak. A locally run Claude setup or an Excel MCP server shares that property; the difference is that Mica delivers it as a packaged app you do not have to assemble. Mica security and privacy documents the local-first design and how to verify it yourself.
The price structures differ as much as the execution models. The cloud three charge a recurring subscription that renews whether or not you touch them in a given month; Mica is free to download and you pay for the batteries you use.
In regions where cloud access is restricted or unstable, the gap widens: ChatGPT and Claude depend on a stable connection to their servers, and cloud processing adds region concerns on top of that. A local desktop app keeps working on the connection you have, because only the model conversation needs the network — local Excel AI, available globally covers the full picture.
How to Choose
- Choose AI-native spreadsheets if you are not tied to Excel at all — Sourcetable and its peers are cloud-first and never touch a .xlsx file.
- Choose ChatGPT for Excel if you already pay for ChatGPT Plus and mostly want formula ideas without switching tools.
- Choose Copilot if you live inside Microsoft 365 and want AI where your data already lives — accepting that your workbook is processed in the cloud.
- Choose Mica if you want the task executed in your workbook with every step shown, and you do not want your files uploaded.
The decision narrows to two questions. Do you need the work done on your machine with the file never uploaded, or is cloud execution with your data uploaded acceptable? And does every step need to be visible and auditable on your own file? Answer both and the table above leaves exactly one row standing.
Frequently Asked Questions
Do any of these run the task in my Excel file?
Yes — ChatGPT for Excel, Claude for Excel, and Copilot's Agent Mode all execute in your workbook with your approval, but they run in the cloud and upload your file. Mica executes locally on your machine, with the file never leaving it — as does Claude run as a local setup or any assistant wired to an Excel MCP server.
Which is cheapest for occasional formula help?
If you only need a formula now and then, a subscription only makes sense if you already hold it — otherwise Mica's free download or a free generator covers occasional use with no subscription cost, and for occasional cloud-executed changes the subscription is the price of admission.
Do all three brands upload my data?
As add-ins, yes — ChatGPT, Claude, and Copilot all process your workbook in the cloud. Mica keeps files on your machine, and so does any local MCP setup; the add-ins are the ones that upload.