Best carbon accounting software in 2026: an honest comparison
The best carbon accounting software in 2026 is the one that gets real activity data out of your organisation with the least chasing, then turns it into Scope 1, 2 and 3 figures you can defend to an auditor. For large UK and EU teams, compare Ella, Greenly, Persefoni, Sweep, Watershed, Plan A and Normative on data collection first.
Last updated 28 October 2026 · By Tom Wilford, Founder, Ella
Get startedWhat is the best carbon accounting software in 2026?
Carbon accounting software compared
| Software | How the vendor describes it | Often shortlisted by | Worth asking in the demo |
|---|---|---|---|
| Ella | AI-native ESG and carbon accounting software built as an agent: collects data from colleagues by email, reads uploaded invoices and bills, connects to systems, and produces SECR, CDP and reduction plan outputs with a source on every number | Sustainability teams at large and fast-growing companies that also need ESG reporting (CSRD, VSME) or EcoVadis support | Show me a colleague being chased for a missing meter reading and the evidence trail behind one number |
| Greenly | A carbon accounting platform that automates data collection and calculates a full Scope 1, 2 and 3 footprint, with an AI assistant for data gaps; says it has 4,000 clients and over 100 software integrations | Companies wanting a guided footprint with expert support | Which of our systems are covered by the integrations, and what is manual |
| Persefoni | Carbon accounting with a financial services product for PCAF-aligned financed emissions, plus a free tier for investee companies to measure their own footprint | Asset managers, banks and investors measuring portfolio emissions | How portfolio company data flows into our financed emissions figures |
| Sweep | A sustainability platform built for enterprises, with workflow-driven data collection across finance, operations, procurement and sustainability teams | Enterprises managing carbon and wider ESG data together | How a new data owner is onboarded and reminded |
| Watershed | An enterprise sustainability AI platform for managing sustainability data, meeting reporting requirements and cutting environmental impact | Corporate climate teams at large companies | How Scope 3 supplier data is requested and refreshed |
| Plan A | Certified software to measure, report and reduce a carbon footprint | Companies in software, business services, fleet, media and fashion | What the certification covers and how reduction targets are tracked |
| Normative | A carbon accounting platform to calculate, report and reduce Scope 1, 2 and 3 emissions, citing 349,000 verified emission factors | Companies that want detailed spend and activity-based calculations | How emission factors are chosen and shown for each line |
What does carbon accounting software actually do?
The part most demos skip: getting the data in
Estimates, data quality and confidence scores
Which reports should carbon accounting software produce?
| Report or framework | Who usually needs it | What the software should produce |
|---|---|---|
| SECR | Quoted companies and large unquoted UK companies and LLPs | Energy use, Scope 1 and 2 emissions, an intensity ratio and a methodology note for the directors' report |
| CDP | Companies asked by investors or large customers to disclose | Climate questionnaire answers backed by Scope 1, 2 and 3 data and targets |
| Carbon reduction plan (PPN 006) | Suppliers bidding for major UK central government contracts | A published plan with Scope 1, 2 and Scope 3 emissions, reduction measures and a net zero commitment |
| UK SRS S2 | Voluntary today; listed companies may be brought in by the FCA | Climate-related disclosures aligned to ISSB, including greenhouse gas emissions |
| CSRD and VSME | EU companies in scope and their value chain suppliers | Climate data points (ESRS E1 or the voluntary standard) alongside wider ESG data |
How to choose carbon accounting software: a demo checklist
| Question to ask | Why it matters |
|---|---|
| Who collects the data, us or the software? | This is where most of the hours in carbon reporting go |
| Can it read invoices and utility bills we upload as PDFs? | Most site data still arrives as documents |
| Can I click any number and see its source document and submitter? | Auditors and assurance providers will ask |
| How does it show which categories rely on estimates? | Tells you where to improve data quality next year |
| What happens to our base year when we acquire a business? | Acquisitions are common at fast-growing companies |
| Which outputs come ready made: SECR, CDP, reduction plan, CSRD? | Avoids rebuilding the same numbers in spreadsheets |
| Does it cover wider ESG and supplier questionnaires too? | One data set for carbon, ESG reporting and ratings saves duplicate requests to colleagues |
Where Ella fits
How Ella helps
Carbon accounting software
Collect energy, travel and supplier data automatically and produce SECR, CDP and reduction plan outputs.
ESG reporting software
Use the same data for CSRD, VSME and wider ESG reporting, with a source on every number.
ESG strategy software
Turn your footprint into targets, a reduction plan and a strategy your board will sign off.
Related resources
SECR Reporting Explained: Who Must Report and What to Include
SECR (Streamlined Energy and Carbon Reporting) requires UK quoted companies, and large unquoted companies and LLPs, to report their energy use and greenhouse gas emissions in their annual report. A company is large if it meets two of three tests: turnover of £36m or more, balance sheet of £18m or more, or 250 or more employees. Scope 3 is optional.
Carbon Reduction Plan Template (PPN 006)
A Carbon Reduction Plan (CRP) is a short public document that suppliers bidding for UK government contracts worth over £5m a year must publish. It commits to net zero by 2050, reports Scope 1, Scope 2 and five Scope 3 categories against a baseline, lists reduction measures and is signed by a director.
CDP reporting explained: how scoring works and why the data is the hard part
CDP reporting means answering CDP's annual environmental questionnaire, usually because an investor or a large customer asked you to. Responses are scored from D- to A across four levels. In the 2026 cycle the scoring deadline was 16 September, and final responses close in the week commencing 26 October.
ESG data collection software: how to collect ESG data without chasing spreadsheets
ESG data collection software gathers the energy, emissions, workforce and governance data a sustainability report needs from the people and systems that hold it. Good tools request data from named owners, chase them, read invoices and bills, pull from integrations, and keep a source on every number so the final report is audit-ready.
Frequently Asked Questions
What is the best carbon accounting software for large companies?
For large companies, the best carbon accounting software is the one that automates data collection across many sites and data owners, keeps an audit trail on every number and produces the reports you owe, such as SECR, CDP and CSRD. Shortlist on data collection first, then on calculation depth and outputs.
What is the best carbon accounting software in the UK?
UK teams should prioritise SECR outputs, carbon reduction plans for PPN 006 bids and readiness for the UK Sustainability Reporting Standards. Ella, Greenly, Sweep, Watershed, Plan A, Normative and Persefoni all serve UK customers. Test each with your own data, including how it handles UK utility bills.
What does carbon accounting software do?
It converts activity data such as fuel, electricity, travel and supplier spend into greenhouse gas emissions using emission factors, sorts them into Scope 1, 2 and 3 under the GHG Protocol, tracks progress against a base year and produces reports for frameworks like SECR, CDP and CSRD.
Is carbon accounting software the same as carbon management software?
The terms overlap. Carbon accounting usually means measuring and reporting emissions, while carbon management software adds reduction planning, target tracking and supplier engagement. Most platforms on this list do both to some degree, so ask to see the reduction planning features in the demo.
Can I do carbon accounting in Excel instead of software?
You can, and many companies start there. Spreadsheets struggle once you have several sites, many data owners, Scope 3 categories and an auditor asking where each number came from. Software earns its cost when it removes the chasing and keeps the evidence trail.
How much does carbon accounting software cost?
Pricing depends on company size, number of sites, Scope 3 depth and which reporting modules you need, and most vendors quote on request. Compare the licence against the hours your team spends collecting and cleaning data today, plus any consultant fees for SECR or CDP.
Which carbon accounting software is best for Scope 3?
Look for software that supports both spend-based and activity-based methods, can request data from suppliers, and shows which of the 15 Scope 3 categories rely on estimates. The right choice depends on which categories dominate your footprint, so map those first.
Can AI tools like ChatGPT or Copilot do carbon accounting?
General AI assistants can explain methods and draft text, but they cannot chase colleagues for meter readings, hold an auditable record of every data point or keep emission factors current on their own. AI-native carbon accounting software such as Ella builds those workflows in.