Two carbon credits from the same project type can be very different in quality. Rating agencies try to tell them apart by studying each project and giving it a grade. Ecosystem Marketplace describes their aim as becoming the equivalent of credit rating agencies in bond marketsSource 7. This guide explains how the main agencies say they rate credits, what their scales mean, and how to use a rating without relying on it alone. It is part of our Quality section.
We describe each agency’s publicly available methodology only. We don’t reproduce individual project ratings.
What is a carbon credit rating?
A rating is an agency’s opinion on whether a project’s credits deliver what they claim. BeZero defines its rating as its current opinion on the likelihood that a given credit achieves a tonne of CO₂e avoided or removedSource 1. Sylvera’s rating assesses the likelihood that a project’s credits have delivered on their claims of avoiding or removing one tonne of carbon dioxideSource 3.
Ecosystem Marketplace counts BeZero, Sylvera, MSCI and Calyx Global among the independent, privately owned rating agencies. It says their methods variously cover additionality, carbon accounting, permanence, operational risk and co-benefitsSource 7.
How the main agencies rate credits
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| Agency | Scale | Main risks assessed | Free to view |
|---|---|---|---|
| BeZero Carbon | AAA to D (8 grades) | Additionality, over-crediting, non-permanence, leakage, perverse incentives, policy and political environment | Headline letter ratings and summaries |
| Sylvera | AAA to D | Carbon accounting, additionality (including over-crediting risk), permanence | Not stated in its framework paper |
| Calyx Global | AAA to D (8 grades) since January 2025 | Additionality, over-crediting, permanence, overlapping claims | Tiered ratings, after registration |
As of Oct 2026
BeZero Carbon
BeZero uses an eight-point scale from AAA to D. AAA means a credit has the highest likelihood of achieving one tonne of CO₂e avoided or removed, AA very high, A high, BBB moderate, BB moderately low, B low, C very low and D the lowestSource 1. Its analysts assess six risk factors: additionality, over-crediting, non-permanence, leakage, perverse incentives, and the policy and political environmentSource 2. BeZero says it monitors rated projects on an ongoing basis and can put a rating on watch when new information may have a material impact on itSource 2. It offers free access to headline letter ratings and rating summaries, with paid access for more detailed ratings and analyticsSource 2.
Sylvera
Sylvera rates projects from AAA, the highest likelihood of delivering on their carbon claims, to D, the lowestSource 3. Its rating combines a carbon accounting score, an additionality score that includes over-crediting risk, and a permanence score. Co-benefits get a separate score that is excluded from the rating, so they can’t inflate the carbon gradeSource 3. Sylvera says its ratings are reviewed regularly and updated when it sees a material change to a project or new dataSource 3.
Calyx Global
Calyx Global moved to an eight-point AAA to D scale on 21 January 2025, replacing a ten-point scale from A+ to E, to make its ratings easier to compare with other agencies’. It said its assessment method didn’t change: its GHG integrity framework still covers additionality, over-crediting, permanence and overlapping claimsSource 4. Calyx Global assesses the carbon-crediting programme, the methodology and the project itselfSource 5. Since June 2025, registered users can see its tiered GHG integrity ratings and project-level SDG impact ratings for free, while the full AAA to D grades are for paying subscribersSource 6.
Why ratings for the same project can differ
The letters look alike, but the methods don’t. Ecosystem Marketplace notes that each agency designed its methodology independently, and calls the methods opaque, so they don’t produce the same results in all casesSource 7. In its survey, 19% of respondents mentioned credit ratings, many of them noting the potential to confuse buyers, while others saw ratings as a sign of a maturing marketSource 7.
Read the definition, not just the letters
An A from one agency is not the same as an A from another. Before comparing grades, read what each agency says its scale measures and which risks it includes.
Ratings vs the CCP label
The ICVCM’s CCP label and ratings answer different questions. The label shows that a credit’s programme and methodology meet the ten Core Carbon PrinciplesSource 8. It is pass or fail. A rating grades an individual project, and agencies such as Calyx Global look at the programme, the methodology and the project togetherSource 5.
The two work well together. Use the CCP label as a minimum bar, and a rating to compare projects that clear it.
How to use ratings when you buy
- Check the rating at the source. If a seller quotes a rating, look it up on the agency’s own site, and check its date.
- Compare like with like. Compare ratings from the same agency, not an A from one with an A from another.
- Look for agreement. If two agencies rate a project very differently, read their summaries to see why.
- Don’t stop at the rating. A rating doesn’t show that credits were retired in your name. Our guide to how to verify carbon credits shows how to check the registry, and high-quality carbon credits lists the other checks.
Quality also affects price: Ecosystem Marketplace lists differences in project quality among the reasons prices vary within a project typeSource 7. See why carbon credit prices differ.