Independent ratings are the closest thing the carbon credit market has to a credit rating for a bond. They help buyers see which projects are likely to deliver the tonnes they claim, and they are increasingly used in procurement criteria.
But carbon credit rating agencies do not all measure the same thing. Some focus narrowly on whether the tonne is real; others add delivery risk, legal risk or co-benefits. Their scales look alike, which makes it easy to compare an A from one agency with an A from another as if they meant the same.
This comparison explains how BeZero, Sylvera, Calyx Global and MSCI rate carbon credits, how to get access, why their ratings differ and how to use them when you buy.
The short answer. All four agencies rate how likely credits are to deliver real climate impact, on letter scales from AAA down. BeZero and Sylvera focus on carbon efficacy; Calyx Global separates greenhouse gas integrity from SDG impact; MSCI adds implementation risks such as delivery and legal risk. Check the rating date and rationale, compare more than one rating where possible, and combine ratings with the CCP label and your own document checks.
The four agencies at a glance
BeZero | Sylvera | Calyx Global | MSCI | |
|---|---|---|---|---|
Scale | 8 points, AAA to D | AAA to D | 8 points, AAA to D (since January 2025), SDG score +1 to +5 | 7 points, AAA to CCC |
Core question | Likelihood that a credit achieves a tonne of CO2e avoided or removed | Likelihood that the project delivers its claimed avoidance or removal | Greenhouse gas integrity, with SDG impact rated separately | Project integrity across emissions impact and implementation |
What it covers | Additionality, over-crediting, non-permanence, leakage, perverse incentives, policy and political environment | Carbon, additionality (including over-crediting) and permanence; co-benefits as a separate score | Additionality, permanence, over-crediting and other integrity factors; SDG contributions separately | Additionality, quantification, permanence, co-benefits, legal and ethical risks, delivery risk |
What it leaves out | Broader project risks such as fraud or default, except where they affect carbon efficacy | Co-benefits are not part of the headline rating | SDG impact is not part of the GHG rating | Combines risks into one rating, so read the breakdown |
Access (checked October 2026) | Headline ratings with a free account | Freemium: some ratings free, full detail by subscription | Public platform since 3 June 2025 with free tiered GHG ratings | Commercial product; check access with MSCI |
Sources: BeZero rating definition, Sylvera ratings terminology, Calyx Global’s new GHG rating scale and public platform, MSCI Carbon Project Ratings. Access models change often; check before you rely on them.
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How each agency approaches a rating
BeZero
BeZero describes its rating as its current opinion on the likelihood that a credit achieves a tonne of CO2e avoided or removed. The focus is deliberately narrow: greenhouse gas efficacy. Broader risks such as fraud, default or business interruption are excluded unless they affect that efficacy, and co-benefits are not a rating factor. That makes a BeZero rating a clean answer to one question: is the tonne likely to be real? Our overview of the highest-rated BeZero credits shows how this plays out by project.
Sylvera
Sylvera rates projects from AAA to D on carbon, additionality (including over-crediting risk) and permanence, using satellite data and machine learning alongside expert review. It publishes a co-benefits score next to the rating, but keeps it out of the rating itself because the rating’s job is to assess whether the claimed tonnes were achieved. See our overview of Sylvera’s highest-rated credits.
Calyx Global
Calyx Global rates greenhouse gas integrity and, separately, the project’s contribution to the UN Sustainable Development Goals. In January 2025 it moved its GHG ratings from a ten-point A+ to E scale to an eight-point AAA to D scale, in line with most of the market, while SDG ratings stay on a +1 to +5 scale. Since June 2025 its platform is public, which makes it one of the easiest ratings to check. Our article on highest-rated Calyx credits shows examples.
MSCI
MSCI’s Carbon Project Ratings, built on the integrity assessment developed by Trove Research, cover more than 4,000 projects on a seven-point scale from AAA to CCC. MSCI combines emissions impact with implementation integrity: alongside additionality, quantification and permanence, it assesses co-benefits, legal and ethical risks and delivery risk. That broader scope means an MSCI rating can be lower than a carbon-only rating for a project with strong climate impact but, for example, governance or delivery concerns.
Why ratings for the same project can differ
Two agencies can rate the same project differently without either being wrong. The main reasons:
Different questions. A carbon-efficacy rating and a rating that includes delivery or legal risk answer different questions.
Different data and models. Satellite analysis, baseline assumptions and leakage models differ per agency.
Different timing. Ratings are updated at different moments; a rating from 2024 may not reflect a 2026 verification or methodology change.
Different treatment of co-benefits. Some keep them separate, some fold them in.
So read the rationale behind the letter, and note the date.
How to use ratings when you buy
Check whether the project is rated, and by whom. No rating is not a verdict; many projects are simply not covered. Ask the supplier which ratings exist.
Read the date and the rationale. The headline letter matters less than the reasons behind it: baseline, additionality, permanence.
Compare more than one rating where possible. Agreement between agencies is a stronger signal than a single rating.
Combine with the CCP label and your own checks. The CCP label covers programme and methodology; ratings cover the project; your checks cover the documents, retirement and contract.
Write it into your procurement. Ask suppliers to list ratings and known criticism (question 11 in our list of supplier questions), and score them as one of several quality inputs.
Tip from Bernard de Wit, Co-founder of Regreener: “A rating is a strong second opinion. Read the one or two pages behind the letter: they tell you which assumption the analyst doubted. That is exactly the question to put to your supplier, and the answer tells you more than the letter does.”
Ratings are one of the inputs in Regreener’s 100+ datapoint quality framework, under compliance and reputation, next to our own assessment of carbon impact, co-benefits and reporting. Our checklist on how to assess carbon credit quality shows where ratings fit among the other checks.
Put ratings next to the other quality points
Regreener’s free Quality Checker lets you enter up to five projects with their rating, CCP status and the other facts you know, and gives you the quality points to verify per project, plus a portfolio overview. If you would like a review of specific projects with ratings from several agencies, talk to a Climate Strategist.
