Excel is still the default tool for many carbon teams. It is flexible, familiar and easy to adapt. For years, it has been used to build carbon models, track emissions and support early-stage assessments.
But expectations have changed. Procurement teams are not just asking for carbon data. They want outputs that can be audited, aligned with cost structures and used to make defensible decisions. That is where Excel no longer fits.
This article explains why spreadsheet-based models are no longer suitable for high-stakes submissions, and what a better alternative looks like.
The Problem with Excel-Based Carbon Models
Most spreadsheet-based carbon models were never designed for external review. They started as internal tools, built quickly to meet reporting needs or support optioneering. Over time, they became more complex, more customised and more fragile.
Today, those same models are being used to support bids, framework submissions and audits. But the requirements have moved on. What was once good enough for internal tracking now needs to stand up in front of procurement teams, commercial reviewers and independent assessors.
That shift creates problems:
- Models are rarely version controlled
- Assumptions are undocumented or scattered
- Classifications do not match cost plans
- Reviewers cannot trace how figures were calculated
This is not a problem with Excel itself. It is a mismatch between the tool and the task.
5 Ways Excel Falls Short in Procurement
When carbon models are used in procurement, the expectations shift. Reviewers want to understand how numbers were calculated, where data came from and whether the output can be trusted. Most spreadsheet-based models cannot meet that standard.
Here are the five most common issues that cause problems during review:
1. No Audit Trails
In a spreadsheet, anything can be changed without leaving a record. Values get overwritten. Formulas get replaced with hard numbers. Comments disappear when versions are saved over.
For a reviewer, this makes it impossible to tell what changed and why. Without version control, structured change logs or traceable calculations, the model becomes a black box. That creates risk, delays review and undermines the credibility of the submission.
2. Misalignment With Cost Structures
Carbon and cost models are often built separately, using different classifications, quantities and package breakdowns. This disconnect becomes a problem when both sets of data are reviewed together.
Procurement teams expect carbon outputs to align with the cost plan. If a carbon figure cannot be matched to a BoQ item or work package, it creates confusion. Reviewers are left guessing how carbon relates to the rest of the submission.
This lack of alignment weakens the bid. It also raises questions about whether the carbon model reflects the latest design, scope or commercial assumptions.
3. High Risk of Error
Spreadsheet-based models are fragile. One broken formula, one copy-paste error or one misaligned cell can distort the entire output, and those errors are hard to spot until it is too late.
This is especially true when multiple people work on the same file, or when models are reused across bids. Formulas get edited. Inputs are updated without checking dependencies. Old data gets left in by mistake.
Procurement reviewers do not have time to investigate every anomaly. If something looks off, they move on. And if the numbers cannot be trusted, neither can the submission.
4. Unclear Lifecycle Scope
Many spreadsheet models report carbon without clearly stating which lifecycle stages are covered, across As, Bs, and Cs. While A1 to A3 is often assumed, reviewers are rarely told what is included, what is excluded or what is estimated, and Bs and Cs are often overlooked altogether.
That creates risk. Frameworks may expect full lifecycle coverage. Clients may be comparing bids based on scope. If your model does not make that scope visible, it looks incomplete, even if the data is valid.
Without clear stage definitions and documented assumptions, reviewers cannot assess whether your output meets the brief. That slows down review or results in penalties.
5. Poor Collaboration and Visibility
Excel models are usually built and maintained by one person or one team. They sit on individual drives, are emailed back and forth, and often exist in multiple slightly different versions. That makes it hard for anyone else to work from the same source of truth.
When carbon and cost teams cannot access or edit the same file, outputs become inconsistent. One version might reflect an old design. Another might include assumptions no one else has seen. This slows collaboration, increases rework and damages confidence in the final submission.
Procurement reviewers notice this. When outputs are inconsistent or clearly built in isolation, the bid loses credibility.
What Stronger Outputs Look Like
Spreadsheets are familiar, but they are no longer enough. High-quality carbon outputs share a few consistent traits, all of which make them easier to review, trust and approve.
Stronger outputs are:
- Built within structured systems, not manual files
- Aligned to commercial classifications like ICMS
- Traceable from quantity to emission factor to final figure
- Clear about scope, stage coverage and assumptions
- Stored in a shared environment with version history and change tracking
These are not just technical upgrades. They reduce review time, prevent miscommunication and improve the credibility of the submission. That can be the difference between a bid that passes and one that gets flagged.
How Sterling Helps Carbon Teams Upgrade from Excel
Sterling gives carbon teams the structure, traceability and alignment that spreadsheets cannot offer. It replaces manual effort with shared workflows and turns carbon data into outputs that hold up in procurement.
With Sterling:
- Build carbon and cost estimates in the same workflow
- Align outputs to ICMS or other BoQ structures
- Track changes with full version history and audit visibility
- Define lifecycle scope and assumptions as part of the model
- Export structured, readable outputs built for review
You are no longer working in isolation. Carbon models reflect the same quantities and scope used by commercial teams. Outputs are always up to date, always traceable and always defensible.
Leaving Excel behind is not about learning a new tool. It is about removing the risks that come with using the wrong one.
Ready to discover the power of Sterling for yourself? Book a free consultation today and find out more.