What does the spend-based minimum really cost?

The cheapest way to produce a Scope 3 number is a spend export, a free factor set and a weekend. For screening a footprint, that is a legitimate method under the GHG Protocol. The question is what it costs to stop there, and the answer is paid in data quality rather than cash.

The shared scenario for this series, ours by assumption rather than sourced: a UK organisation with 10,000 suppliers in its accounts payable export, committed to Scope 3, reporting annually. The 10,000 is the purchase ledger rather than an engagement list: most teams actively engage a few hundred suppliers, but Scope 3 Category 1 brings the whole ledger into the inventory, so the calculation, spend-based or otherwise, runs across every line. The same trade-off applies to portfolio companies.

What does the spend-based minimum cost in cash?

Almost nothing, which is its entire appeal. The UK government conversion factors are published free by DESNZ under the Open Government Licence, most recently the 2026 edition in June 2026. The US EPA's Supply Chain GHG Emission Factors are a public download. The labour is mapping spend categories to factors and multiplying, and our assumption is that half a data analyst covers it: roughly £27,000 a year, being half of Robert Half's 2026 UK median base salary of £48,250 plus employer National Insurance at HMRC's published 15% rate. The assumption is ours; the salary and the rate are published.

What can a sector average not do?

Tell two suppliers apart. A sector-average factor gives every company in a category the same rate per pound of spend, so the supplier who has decarbonised and the supplier who has not produce an identical line in your inventory. Two consequences follow. Your hotspots are really just your biggest invoices, which you already knew. And a supplier who cuts their emissions changes your number not at all, so there is nothing to say to the suppliers you engage, and no way to show progress that is not a change in what you bought. To be clear about the axis: spend is a perfectly good input, and the problem is the generic factor applied to it, not the ledger it came from.

What does it do to the target?

The published record says the problem is a blocker, not a rounding error. The Science Based Targets initiative's survey with BCG, February 2023, from 230 responding organisations, found only 6% of emission factors in use were supplier-specific, and 85% of respondents saw data access as a barrier to a usable baseline. In financial services, where the equivalent of the sector average is a low PCAF data quality score, usually shortened to DQ score, KPMG's June 2025 benchmark of 33 major banks records the sharpest version: "Some banks do not disclose financed emissions targets where data quality scores are higher than 4, due to a high risk of restatement." The minimum produces a number, and then the number cannot carry a target.

What does it cost when you upgrade later?

A restatement, by obligation rather than choice. The GHG Protocol Corporate Standard requires base year recalculation for changes in calculation methodology or improvements in the accuracy of emission factors or activity data that have a significant impact. Moving from sector averages to company-specific figures is exactly such an improvement, so a baseline built on the minimum has a restatement scheduled into it from day one. The same SBTi survey found 70% of organisations had re-baselined within five years, half of those, so 35% of all respondents, for methodological reasons. Starting minimal does not avoid the work. It timetables it.

When is the minimum the right answer?

As a first pass. Screening a footprint with spend and free factors is how you find out where the emissions are before spending anything, and the GHG Protocol treats it as a legitimate starting method. If this is year one and the job is to locate the hotspots, the minimum does that. It stops being the right answer the year the number has to support a target, a supplier conversation or an auditor's question.

What does the same spend file produce with better factors?

The upgrade does not require new inputs. DitchCarbon provides verified emissions data for over 2 million organisations, so procurement, sustainability and finance teams can measure and act on supply chain and portfolio emissions from one source. The same spend export, imported as it is, calculates against organisation-specific figures wherever a company has disclosed, at no extra effort on your side; activity and product level data go further and do cost real effort, which is why they come after, not first. Coverage gaps are shown, not hidden, so the remaining sector-average lines are visible and become the engagement list rather than the whole inventory.

To see the difference on your own numbers, send a sample of your supplier list to the coverage check and compare how many lines move off the sector average.

This post is part of a series pricing the alternatives to buying supplier emissions data, all on one shared scenario: collecting it manually, consultants every cycle, doing nothing, and building the platform in house.

Last reviewed August 2026.