The Concrete Problem: Merging Excel and PowerPoint with Copilot
Every quarter, the same task comes up: export a Microsoft Forms form to Excel, then inject the data into a PowerPoint template to announce the winners of an internal recognition program. Simple on the surface, but this operation involves data cleanup (name deduplication), formatting preservation, and dynamic content per slide.
Three Copilot entry points exist in the Microsoft 365 ecosystem for this type of work:
- Copilot Chat (included in the Microsoft 365 Copilot license, no additional usage cost)
- Copilot Cowork (formerly Copilot Studio Agent, billed in credits)
- Copilot in PowerPoint (integrated directly into the client, included in the M365 Copilot license)
The objective: determine which product delivers the best result, for what cost, with the same prompt.
Source Files and Starting Prompt
The two files used are identical for all three tests:
- An Excel file exported raw from Microsoft Forms (without any manual transformation)
- A PowerPoint template containing parameterized slides: nominee name, nomination details, winner slide
The prompt submitted to all three tools is equivalent:
Attached is the template for presenting the Buddy's Best Awards. Also attached is the Excel with the submissions for this quarter. Update the template by placing the Excel data into the deck. Preserve the look and feel of the PowerPoint. Just put in the new data. For example, if there's an entry for Bob and Bob Smith, assume they are both for Bob Smith. This month the winner was Buddy.
Second notable constraint: the prompt does not specify the exact quarter number — an intentional trap to observe how each engine handles contextual ambiguity.
Watch Out for Session Management
With Copilot Chat, do not close the tab before processing is complete. If you navigate away from the page before the response is finished, the generation is lost and unrecoverable.
Copilot Chat: The Test Surprise
Copilot Chat handles the request by generating internal code to manipulate the PowerPoint file — it has no native knowledge of PPTX format, but circumvents this limitation through automatic scripting.
Observed results:
- Nominee slides are created correctly, one per person
- Deduplication works: entries Buddy and Buddy Young are properly merged
- Formatting is globally preserved, with slight font size reduction
- Quarter number is correctly inferred (Q3 → mention of Q4 for subsequent nominations)
Notable point: Copilot Chat's performance on this type of task has significantly improved in recent weeks. An identical test conducted a few weeks earlier produced degraded formatting. The regression has become measurable improvement — illustrating the pace of continuous deployment of underlying models.
Cost
Copilot Chat incurs no additional credit cost for a tenant with an active Microsoft 365 Copilot license. This is the entry point to test first.
Copilot in PowerPoint: Native Integration, Mixed Results
The Copilot integrated into the PowerPoint client shares the same engine as Copilot Chat, but benefits from PPTX-specific capabilities: it understands slide structure, placeholders, and themes.
In this test, the Excel file is loaded directly into the Copilot panel, with the template already open in the background.
Observed results:
- Quarter number correctly identified (Q3)
- No duplicates in nominee slides
- Font size issue: injected text is too small, affecting readability in presentation
- Winner slide correctly generated
On this dataset, Copilot in PowerPoint falls behind Copilot Chat on formatting fidelity, despite its native PPTX capabilities. The result remains usable with minor manual adjustments.
Copilot Cowork: Persistence and Credit Cost
Cowork relies on a different orchestration engine, designed to handle long, iterative, multi-step tasks. It persists through intermediate errors and can chain complex sub-tasks — making it historically the preferred tool for structured content generation.
First Run: Automatic Model (GPT 4.5)
Cowork automatically selects GPT 4.5 for this task. Results:
- Slightly better formatting than Copilot Chat on some slides
- Incorrect quarter number (Q1 instead of Q3) — ambiguity unresolved
- No duplicates
- Cost: 123 credits
Second Run: Opus 5 Model (Premium)
For comparison, the same test is re-run forcing the Opus 5 model.
Results:
- Visual quality equivalent to previous run
- Same quarter error (Q1)
- Cost: 113 credits — slightly lower, with no measurable quality gain
| Criteria | Copilot Chat | Cowork (auto) | Cowork (Opus 5) | Copilot PowerPoint |
|---|---|---|---|---|
| Cost | 0 credits | 123 credits | 113 credits | 0 credits |
| Formatting | Good | Good | Good | Font too small |
| Name deduplication | Yes | Yes | Yes | Yes |
| Quarter number | Correct | Incorrect | Incorrect | Correct |
| Winner slide | Yes | Yes | Yes | Yes |
| Native PPTX knowledge | No | No | No | Yes |
Recommendation on Model Choice
Leaving Cowork in auto mode is the best default option. Forcing a higher model like Opus 5 provides no quality gains on moderately complex tasks and doesn't significantly save credits either.
Automate the Task with a Custom Copilot Skill in PowerPoint
Beyond the one-time test, the operational objective is to make the task repeatable effortlessly each quarter. Cowork recently gained the ability to define custom skills for PowerPoint and Excel — a feature distinct from classic Cowork skills.
Here's how to create and use this skill directly from the Copilot panel in PowerPoint:
Open the PowerPoint Template and Activate Copilot
Open the template file in PowerPoint, then click the Copilot icon in the bottom right to open the panel.
Access Skills Management
Click the ellipsis (…) at the top right of the Copilot panel, then select Manage skills. You'll find native Microsoft skills (Visualize the slide, Review this presentation, Prepare) as well as a space for Custom skills.
Create a Custom Skill
Click Edit on an existing skill or create a new one. Fill in:
- Name: short, memorable name (e.g.,
Buddy's Best in Show) - Description: summary of the objective — this guides skill triggering
- Instructions: detailed text block (~80 lines) covering expected inputs, deduplication rules, generation instructions, elements not to modify (agenda), winner handling, etc.
Generate Instructions with Copilot
To write the instructions block, submit the template file to Copilot Chat and describe the task. Ask it to generate skill instructions in the expected format. Copy and paste the result into the skill's Instructions field.
Use the Skill Each Quarter
Open the template, load the new Excel export, then simply type:
1Refresh this deck with the latest Buddy's Best data.The skill takes over, asks necessary questions (quarter, winner), and generates the complete presentation.
Custom Skills Storage
Custom skills created in Copilot PowerPoint are stored as .md files in a Copilot > Skills folder in your OneDrive. They follow your account and remain accessible from any computer.
Current Limitation of PowerPoint Skills
Unlike Cowork skills, custom skills in the Copilot PowerPoint panel do not allow attaching supplementary files (images, branding files, assets). If your process requires integrated static resources, Cowork remains more suitable.
Key Takeaways
- Copilot Chat produces results comparable to Cowork on moderately complex tasks, without consuming credits. Test it first.
- Copilot in PowerPoint benefits from native PPTX capabilities but can produce formatting issues (font size) that skill instructions allow you to correct.
- Cowork remains relevant for complex workflows or when orchestrator persistence makes the difference. Anticipate its credit cost — verify credit availability before launching a session at period end.
- Forcing a premium model (Opus 5, GPT 5.5) on a simple task doesn't improve quality and doesn't save credits. Leave it in auto mode.
- Copilot Chat quality is improving rapidly. An unsatisfactory result tested weeks ago may be acceptable today. Regularly retest use cases you've dismissed.
- Custom skills in Copilot PowerPoint transform a repetitive task into a guided process: the user loads the file, types a sentence, answers two questions — and the presentation is generated.
