Which <em>carbon accounting software</em> should you pick in 2026?
A big customer wants your emissions data, an investor asks for a CDP response, your EU subsidiary falls under new rules. The software won't do the work for you, but the wrong one will cost you a year.
The short answer: to measure your footprint without paying anything, start with Persefoni Pro, free for one user across scopes 1, 2 and 3. If you report to several frameworks across countries, look at Sweep. If your scope 3 involves thousands of suppliers, look at Watershed. For a small or mid-size company with European operations, Greenly is the most complete. The rest of this page explains why, where each one falls short, and what to ask in the demo, because none of these vendors lists the price of its full plan.
The ranking is editorial: a sponsored spot is always labeled on its card, and no affiliate link changes a score.
The right carbon platform for your situation
Pro plan free with no time limit: scopes 1, 2 and 3, all 15 scope 3 categories, one user
Best for multi-framework reportingCSRD, ISSB, CDP, GRI, California SB 253 and UK SRS in one platform
Best for large supply chainsFlexible scope 3 from spend, activity or supplier data
Best for SMBs with EU operationsCarbon footprint, life cycle analysis and ESG reporting, with a published price range
Best for full CSRD reportingDouble materiality, ESRS alignment and a CSRD gap analysis
Best EU-hosted optionSpanish vendor, EU hosting and ISO 27001
The 7 carbon accounting platforms, side by side
The rank follows what a US buyer usually needs first (a free inventory, then multi-framework reporting, then supply chain scale), not the score: the score rates each tool on its own, the rank orders them for this market. The "Frameworks" column answers the first question to ask yourself: what are you actually being asked to produce? A supplier questionnaire doesn't need the same tool as a full sustainability report.
| Best for | Frameworks | Free plan | Team size | Visit | ||||
|---|---|---|---|---|---|---|---|---|
| 1 | Persefoni | Best free option | GHG Protocol scopes 1 to 3; CSRD, ISSB, CDP reports as paid add-ons | 4.1/5 | Pro free | ✓ | Any size, one user | Visit → |
| 2 | Sweep | Best for multi-framework reporting | CSRD, ISSB, CDP, GRI, SB 253, UK SRS | 4.0/5 | Custom quote | — | Mid-market and enterprise | Visit → |
| 3 | Watershed | Best for large supply chains | Carbon accounting, supplier scope 3 | 3.9/5 | Custom annual contract | — | Enterprise | Visit → |
| 4 | Greenly | Best for SMBs with EU operations | Bilan Carbone®, VSME, CSRD, TCFD | 4.3/5 | Custom quote | — | SMBs and mid-market | Visit → |
| 5 | Tennaxia | Best for full CSRD reporting | CSRD, ESRS, VSME, double materiality | 4.0/5 | Custom quote | — | Mid-market and enterprise | Visit → |
| 6 | Dcycle | Best EU-hosted option | Scopes 1 to 3, CSRD | 3.8/5 | Custom quote | — | SMBs and enterprise in Spain | Visit → |
| 7 | Carbo | Best for very small French teams | Bilan Carbone®, VSME | 4.2/5 | Start free, paid plans on quote | ✓ | Very small businesses in France | Visit → |
Prices read on each vendor's official pricing page in 2026, excluding tax. "Custom quote" means no amount is listed: only a demo gets you a number.
Is your tool missing from this page? Email us: hello@hackceleration.com
How we compared these platforms
Search for "best carbon accounting software" and look at who writes the lists. Several are published by vendors who rank themselves first. The prices quoted elsewhere usually come from marketplaces or review sites, not from the vendors. Very few explain which framework you actually need.
We compared each vendor's official pricing and product pages, the rules that create the reporting duty, and user feedback from review sites and forums. A platform gets ranked only if we have verifiable facts about its offer or solid user feedback. Watershed and Dcycle list no prices: their cards say so and their scores reflect it. Tools we could barely verify are listed further down, unranked.
- Framework coverageGHG Protocol, CDP, ISSB, CSRD, SB 253: the tool has to produce the report you owe, or nothing else matters.30 %
- Scope 3 and supplier dataScope 3 depends on supplier data and is the hardest part to collect. It's where most projects stall.25 %
- Pricing transparencyA real free tier, a published price point, 12-month commitments, per-entity pricing: what you know before the demo.20 %
- Self-serveCan your team run it alone, or do you need a consultant on top of the license?15 %
- Data qualityWhich emission factors the tool uses, whether it shows uncertainty, whether an outside body has audited its method.10 %
No affiliate link changes a score or a rank.
Reporting thresholds and carbon software plans keep moving. Get the changes before your next reporting cycle
Persefoni
Persefoni is a US vendor, and the only one in this ranking with a genuinely complete free plan. Pro covers scopes 1, 2 and 3, including all 15 scope 3 categories of the GHG Protocol, an AI assistant called Copilot, and a guided Sustainability Report Builder for CSRD, ISSB and CDP. There's no trial period and no time limit. Assets and reporting years are unlimited.
The limits are spelled out. One user only. Annual calculation only. Exporting the emissions summary is a paid add-on, as are the CDP, SECR, CSRD and ISSB reports. Support is self-serve. For more seats, filing-ready reports or reduction modeling, you move to Advanced, which is quote-only and adds SOC 2.
That makes Pro the smartest first step for most companies: you learn where your big emission sources are before any sales call. It's not the end point if you need many contributors or a report you can file as is.
- Scopes 1 to 3 free, with no time limit
- All 15 scope 3 categories
- AI assistant to classify your data
- ✓The only full free tier in this ranking
- ✓Unlimited assets and years
- ✓Upgrade to Advanced without switching tools
- ✗One user on Pro
- ✗Emissions summary export is paid
- ✗Self-serve support only
The best way to measure before you sign anything. Run your first calculation in Pro, then compare other vendors' quotes knowing exactly where your emissions sit.
Sweep
Sweep describes itself as software that helps companies track and act on their ESG and carbon emissions. It targets three segments: enterprise, mid-market and financial institutions. Its real edge is the list of frameworks it supports: CSRD, ISSB, California SB 253, UK SRS, CDP, PCAF for financed emissions, GRI, SFDR and SASB.
If you report in several jurisdictions, that's the deciding factor: one data collection, several reports. Independent reviewers point out the flip side. For a small team with no sustainability lead, Sweep is oversized, and reviewers report per-employee pricing that climbs fast with headcount.
No price, no trial, just a demo. The Starter plan suggests a lighter entry point, but nothing about it is published.
- CSRD, ISSB, SB 253, UK SRS, CDP, GRI, SFDR, PCAF
- Dedicated offer for financial institutions
- Carbon and ESG data in one place
- ✓The widest framework coverage here
- ✓One collection, many reports
- ✓Fits multi-country groups
- ✗No public pricing
- ✗Reviewers report per-employee pricing
- ✗Too heavy without a sustainability lead
The pick if you publish across several countries and frameworks. If you only need a GHG inventory, Persefoni Pro covers it for free.
Watershed
Watershed is a US platform built for large accounts. There's no public price: it's a negotiated annual subscription. It shows up in most US rankings of carbon accounting software.
Users mostly praise how flexible its scope 3 is. You can calculate it from spend, from activity data or from data your suppliers send, and blend the three. The interface also gets good marks (around 4.5 out of 5 on a small number of reviews).
The main complaint is supplier onboarding. It gets little hands-on help, and with a large supplier base you end up buying extra services. Reviewers who look at small teams call it oversized.
- Scope 3 from spend, activity or supplier data
- Well-liked interface
- Built for enterprise
- ✓Very flexible scope 3
- ✓Strong user ratings
- ✓Handles large supplier bases
- ✗No public pricing
- ✗Little help onboarding suppliers
- ✗Out of reach for small companies
Worth a look only if your scope 3 spans thousands of suppliers. Ask for the supplier onboarding services to be priced in the demo, not just the license.
Greenly
Greenly is a French vendor with a strong presence among European SMBs. The platform covers a full carbon footprint under the French Bilan Carbone® method, product life cycle analysis, and an ESG module for CSRD, VSME and TCFD. Scopes 1 and 2 are measured from physical data (fuel, kWh). Scope 3 starts from spend and moves to physical data over time.
Beyond measurement, Greenly sells what comes next: action plans, reduction pathways, supplier engagement. The three plans move up in that order, and the middle one is labeled the most popular. None shows a price. Bundles for several entities come with a discount.
User ratings are good (around 4.7 out of 5 on the big review sites). The complaints are consistent: expensive for a very small company, support sometimes slow, prebuilt reports you can't customize.
- Carbon footprint, life cycle analysis and ESG reporting in one tool
- Scope 3 from spend, then physical data
- A price range published by the vendor
- ✓Covers the path from footprint to action plan
- ✓Built for SMBs and mid-market
- ✓Multi-entity bundles
- ✗No trial, demo required
- ✗Pricey for a very small business
- ✗Prebuilt reports hard to customize
A strong pick if you run European entities and want one tool from footprint to reporting. Ask for the per-entity price and the second-year price in the demo.
Tennaxia
Tennaxia is a French vendor of non-financial reporting software. It guides reporting across several frameworks (CSRD, VSME and others), maps data to the ESRS standards, builds the double materiality matrix and calculates scopes 1 to 3.
The most useful module to start with is CSRD Gap Analysis: it compares the data you already hold with what the ESRS require and shows the gaps. Traace is the carbon brand attached to Tennaxia.
Tennaxia claims no software certification, which is the honest position. It talks about footprints built to ABC, CDP and GHG Protocol standards. No price, no trial.
- Double materiality matrix
- ESRS gap analysis
- Scopes 1 to 3 carbon footprint
- ✓Built for full CSRD reporting
- ✓Several frameworks in one tool
- ✓No inflated certification claims
- ✗No public pricing
- ✗Oversized outside CSRD scope
- ✗Needs a team to feed it
The right tool if your EU entities still exceed the CSRD thresholds. Ask whether advisory support is included or billed on top.
Dcycle
Dcycle is a Spanish vendor. It calculates scopes 1 to 3 and prepares CSRD reporting. It holds ISO 27001 (information security), follows the GDPR and hosts data in the EU. It also advertises no long-term commitment.
Named customers range from industry to banking: ABB, Ajinomoto, Eiffage, KLN, Sabadell, Valeo. BBVA offers its customers 15 % off Dcycle.
No plan names, no prices. For US-only reporting, Persefoni or Sweep fit better. For a Spanish subsidiary, Dcycle knows the local ground.
- EU hosting, ISO 27001
- No long-term commitment advertised
- 15 % off for BBVA customers
- ✓European vendor
- ✓Industrial references
- ✓Good fit for a Spanish subsidiary
- ✗No public plans or prices
- ✗Less relevant for US-only reporting
- ✗Few user reviews in English
The right call for Spanish operations or EU hosting requirements. For a US inventory, start elsewhere.
Carbo
Carbo is a French tool built on the Bilan Carbone® method, a French method compatible with the GHG Protocol. Start is free but only measures your digital usage: an entry point, not a footprint.
The real product starts with Essentiel: a footprint across the three scopes, online help, guided setup, bulk import, and a footprint presented as audited and compliant. Premium adds several users, a dedicated carbon coach, internal data collection campaigns, targets and an action plan. A VSME reporting feature helps answer customer questionnaires.
French users rate it very highly (4.9 out of 5, 90 % would recommend), on a small number of reviews. Value for money is its lowest mark, at 4.4.
- Bilan Carbone® method
- VSME reporting for customer questionnaires
- Unlimited footprints during the 12 months
- ✓Very simple for a first footprint
- ✓Dedicated coach on Premium
- ✓Very satisfied users
- ✗Free plan covers digital only
- ✗Paid plan prices not listed
- ✗French market focus
Only relevant if you have a small French entity that owes a Bilan Carbone®. For everything else, start with Persefoni Pro.
What are you actually being asked for?
Before you compare platforms, name the document someone expects from you. Plenty of companies buy an enterprise ESG suite when all they owe is a customer questionnaire. In Europe, the Omnibus package narrowed the CSRD sharply, but customers keep asking suppliers for data.
A customer sends you a supplier questionnaire
The most common case. You need a clean GHG inventory across scopes 1, 2 and 3, and a way to hand it over. Persefoni Pro calculates it for free, but exporting the emissions summary is a paid add-on: budget for it or use a paid tool for the deliverable. If the customer is European, its questions often follow the VSME, a voluntary standard for small companies.
Investors or customers want a CDP response
If a customer or investor points you to CDP, check the export first. Persefoni sells CDP reports as an add-on; Sweep lists CDP among its supported frameworks. Ask for a sample export before you sign.
You report under California or UK rules
California SB 253 is a state climate disclosure law, and UK SRS are the UK's sustainability reporting standards. Sweep is the only platform here that lists both by name on its pricing page. This page doesn't cover who falls under each rule: check that with your counsel, then put the framework question first in every demo.
You have large EU entities: the CSRD
After the Omnibus, the CSRD only covers companies above both 1,000 employees and €450 million in revenue. Those need double materiality and ESRS data points: Tennaxia, Sweep or Greenly's ESG module.
Your supply chain is huge
When scope 3 means thousands of suppliers, supplier data collection becomes the whole project. Watershed is built for this, but price the onboarding services, not just the license.
Nobody is asking yet
Start with Persefoni Pro. You'll know where your big emission sources are before you talk to a sales team, and you'll negotiate better later.
- Write down the exact document you owe: questionnaire, CDP, SB 253, CSRD.
- List your legal entities: pricing is often per entity.
- Name your three biggest sources: energy, purchases, freight.
- Ask for a sample export in the format you'll file.
- Check whether the plan needs one seat or ten.
How much does carbon accounting software cost?
Everyone asks, and almost no list answers, for a simple reason: hardly any vendor publishes a price. Here are the only figures the vendors put out themselves, and what to ask for the rest.
$0: Persefoni Pro
Free with no time limit, for one user, across all three scopes, with annual calculation. The emissions summary export costs extra. It's the only full free tier in this ranking. Carbo Start is free too, but it only covers digital usage.
A published range: Greenly
Greenly puts a small business footprint at €2,000 to €10,000 on a 12-month subscription per entity, depending on how complex the sector is. A consulting firm is cheaper to measure than a manufacturer with hundreds of suppliers.
Everything else: quote-only
Sweep, Watershed, Tennaxia, Dcycle and Persefoni Advanced all go through a demo. The figures floating around on marketplaces and review sites don't come from the vendors: don't budget from them, use them to negotiate.
- Ask for per-entity and multi-entity pricing.
- Get the second-year price, not only year one.
- Ask what advisory or onboarding services cost if they aren't included.
- Check the commitment length before signing.
- Ask whether your bank has negotiated a discount (BBVA has, with Dcycle).
What sustainability leads wish they'd known first
These tips come from user reviews, forum threads and vendor pages. They matter more than which logo you pick.
Nobody "certifies" carbon software
TrapThe GHG Protocol doesn't certify software. In France, neither the environment agency nor the association behind the Bilan Carbone® method does: the association runs an audit called "Bilan Carbone® Conform", and only audited tools show its logo. If a sales rep says "certified", ask for the audit document.
- Ask for
- The audit document
Scope 3 is the real work
WorkloadScope 3 covers emissions from what you buy, how goods move and how your products are used. It depends on supplier data and takes the longest to collect. Reviews keep saying supplier onboarding gets little help in most tools. Start with your ten biggest suppliers, not all of them.
- Starting point
- Your 10 biggest suppliers
Measure for free before the demo
SavingsRun a first pass in Persefoni Pro with your energy bills and your purchase ledger. You'll walk into demos knowing your main sources, and you'll spot a module you don't need.
- Tool
- Persefoni Pro, free
Five questions for every demo
NegotiationWhich emission factors does the tool use? Does it show uncertainty? Can it export the exact format you file? Has an outside body audited its method? What do onboarding and extra entities cost? Write the answers down so you can compare.
- Questions
- 5
Count the seats you need
CostPersefoni Pro has one user. Carbo adds users only in Premium. If facilities, procurement and finance all need to enter data, the free or entry plan won't hold, so price the plan that fits your real team.
- Check
- Seats included per plan
Measuring doesn't cut anything
OutcomeA recurring point on developer forums: measuring scopes 1, 2 and 3 doesn't reduce a single ton by itself, and there are a lot of carbon accounting tools out there. Pick one that helps you build a costed action plan, and commit to two or three concrete actions from the first inventory.
- Goal
- 2 or 3 actions from year one
Other tools you'll come across, and why they aren't ranked
These platforms show up in other lists. We couldn't verify enough on their official pages to score them.
Plan A: a German vendor on quote
QuotePlan A ranks itself first in its own buyer's guide. Its plans are quote-only. The few user reviews find it steep for a small company just getting started. Compare it only once you hold a Sweep or Greenly quote.
- Price
- Custom quote
Normative: a Swedish carbon accounting tool
QuoteNormative is a Swedish carbon accounting vendor that doesn't publish its plans. We couldn't review its official pricing page, so it stays unranked until we do.
- Price
- Custom quote
Toovalu: check it in a demo
To checkToovalu appears in French carbon software directories. We couldn't read its official site. If you consider it, run the five demo questions above.
- Status
- Unranked
Need more than carbon data? Go here
This page ranks carbon accounting and ESG software. These pages go further on related finance needs.
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Carbon accounting software · FAQ
What is the best carbon accounting software?
It depends on what you owe. To measure for free, Persefoni Pro. For several frameworks across countries, Sweep. For a supply chain with thousands of suppliers, Watershed. For a small company with EU entities, Greenly. Start from the report you must produce, not from the brand.Is there free carbon accounting software?
Yes. Persefoni Pro is free with no time limit and covers scopes 1, 2 and 3 for one user, including all 15 scope 3 categories. Calculation is annual, and the emissions summary export plus CDP, CSRD and ISSB reports are paid add-ons, so handing a file to a customer costs extra. Support is self-serve.How much does carbon accounting software cost?
Almost no vendor publishes a price. The two public reference points are Persefoni Pro at $0 and Greenly's own range of €2,000 to €10,000 for a small business footprint, on a 12-month subscription per entity. Everything else is quote-only, so ask for per-entity and second-year pricing.Do I need to report scope 3?
Often yes in practice, even when no law forces you: large customers ask for it because your emissions are part of their scope 3. Start with your biggest suppliers and spend categories rather than trying to cover everything at once.Does the CSRD still apply to my company after the Omnibus?
Only if you exceed both 1,000 employees and €450 million in revenue. Below that, you're out of scope, and a CSRD customer can't demand more from a supplier under 1,000 employees than what the voluntary VSME standard covers.Can I do my carbon footprint myself with software?
Yes, for a company with simple operations: Persefoni Pro handles the calculation for free (the export is paid). Once your scope 3 depends on many suppliers, or you must file a formal report, guided onboarding or an advisor helps avoid boundary mistakes.What does "certified" mean on carbon software?
Usually nothing official. The GHG Protocol doesn't certify software. In France, the association behind the Bilan Carbone® method audits tools under a program called "Bilan Carbone® Conform", which is not a state certification. Ask the vendor for the audit document.
