How much does a carbon footprint assessment cost and how to finance it? (Diag Décarbon'Action)

Quick answer. A carbon footprint assessment (GHG diagnosis) costs between €4,000 and €12,000 excluding tax for an SME, depending on the scope (scopes 1, 2, 3) and support chosen. The Diag Décarbon'Action scheme, financed by Bpifrance and ADEME, covers 40% of costs, reducing your out-of-pocket expense to €6,000 excluding tax for a flat fee of €10,000. Other subsidies (ACT Pas à Pas, Tremplin) can finance up to 80% of the diagnostic. In 2026, most SMEs can access a comprehensive carbon assessment at a manageable cost.

A carbon footprint assessment is not yet mandatory for all SMEs. Only companies with more than 500 employees must produce a Greenhouse Gas Emissions Report (BEGES) every four years, under article L.229-25 of the Environmental Code. However, two developments strengthen the business case for a voluntary diagnostic in 2026:

1. The CSRD (Corporate Sustainability Reporting Directive) requires large enterprises to ask their suppliers and subcontractors to measure their carbon footprint. An SME without a carbon assessment risks losing contracts with major customers.

2. Public subsidies are expanding. The French government (via ADEME and Bpifrance) offers substantial grants to finance an initial diagnostic, including for very small businesses.

Anticipating a carbon assessment thus becomes both a competitive advantage and a financial opportunity.

The cost of a carbon footprint assessment varies widely. There is no single tariff, as each diagnostic depends on the complexity of your value chain.

For a very small or small SME (1-50 employees)#

For a mid-size SME (50-250 employees)#

For a mid-cap company (250-500 employees)#

Rough guide: a consulting firm or specialist provider typically charges between €1,200 and €2,000 per day of expertise, distributed over 5 to 12 days depending on scope.

The flagship scheme for financing a first carbon assessment in 2026 is Diag Décarbon'Action, jointly managed by Bpifrance and ADEME.

Flat fee and financing#

• Total diagnostic cost: €10,000 excluding tax
• Public subsidy: €4,000 excluding tax (40%)
• Your cost: €6,000 excluding tax
• Duration: 6 to 8 months (12 expert days distributed)

Deliverables included#

The flat fee includes:

• Full scopes 1, 2 and 3 diagnostic
• Mapping of emission sources
• Quantified action plan with at least 40% reduction over 3 years
• Presentation to management
• Complete documentation of assumptions and emission factors

Eligibility criteria#

To qualify for Diag Décarbon'Action, you must meet all of the following criteria:

1. Size: fewer than 500 employees (mid-cap and large companies excluded if ≥ 500 employees)
2. Location: company registered in mainland France or overseas territories
3. Sector: all business sectors welcome
4. GHG history: no greenhouse gas assessment completed in the past 5 years
5. Compliance: current with tax and social contributions
6. Track record: at least 1 year of operational activity

Application process#

The application is lightweight and straightforward:

1. Access the form: https://diag.bpifrance.fr/diag-decarbon-action
2. Completion time: approximately 30 minutes
3. Response time: 2 to 4 weeks
4. Support: a Bpifrance project manager will guide your choice of provider
5. Launch: sign diagnostic agreement and start work

If you have already completed a carbon assessment in the past 5 years, or if you are seeking additional funding, several schemes exist.

ACT Pas à Pas (ADEME, up to 80%)#

• Rate: up to 80% of diagnostic cost
• Maximum amount: €18,000
• Scope: initial or in-depth assessment for engaged enterprises
• Advantage: more favorable rate than Diag Décarbon'Action, but more demanding process

Tremplin for Ecological Transition (status: suspended end 2025)#

This ADEME program offered up to 80% financing, but new applications stopped being accepted from end 2025. Previous projects may be maintained under conditions.

Regional and local government support#

Many regions (Île-de-France, Provence-Alpes-Côte d'Azur, Hauts-de-France, Nouvelle-Aquitaine) offer additional co-financing for ecological transition studies.

Micro-enterprises and self-employed#

Micro-enterprises are not explicitly excluded from Diag Décarbon'Action, provided they meet the criteria (fewer than 500 employees, no assessment in past 5 years). However, the €10,000 cost may seem high for very small turnover. Other schemes (Health Insurance support, regional assistance) may be more accessible.

Groups and holdings#

If you have subsidiaries or branches, the 500-employee threshold applies per separate legal entity, not at group level. Each subsidiary may potentially qualify if it meets the size requirements.

Companies with prior diagnostics#

If you completed a GHG assessment between 2021 and 2026, you are not currently eligible for Diag Décarbon'Action. You will need to wait 5 years after your last assessment. However, you can access other funding programs (ACT Pas à Pas, strategic support, decarbonization investments).

Multinational enterprises with French holding#

If your holding is in France but operations are spread internationally, only scope 3 emissions (upstream and downstream purchases) and scopes 1-2 from French entities will be included in Diag Décarbon'Action. Emissions from foreign subsidiaries are not covered by the French scheme.

Confusing carbon assessment with CSRD reporting#

A carbon assessment is a technical diagnosis of your GHG emissions. The CSRD requires broader reporting covering social, environmental and governance issues (ESG pillar). A carbon assessment is one building block of CSRD reporting, not its equivalent.

Ignoring scope 3, the most data-intensive#

Scope 3 often represents 80 to 90% of an SME's emissions (purchases, transport, business travel). Many companies consider a simplified diagnostic covering scopes 1-2 only, thinking to save money. Mistake: Diag Décarbon'Action mandates all three scopes. Don't try to circumvent: it is necessary for genuine reduction strategy.

Overlooking data quality#

A quick diagnostic (2-3 weeks) will be less reliable than an 6-8 month diagnostic with intensive data collection. Demand that the provider request gas, oil, electricity invoices, airline tickets, and mileage logs from you. Measured primary data always beats default data.

Settling for an action plan without follow-up#

A carbon assessment is useless if not tracked. Diag Décarbon'Action delivers a quantified action plan, but it is up to you to manage it. At Hayot Expertise, we recommend annual review and target adjustment.

Recently, an industrial SME with 80 employees asked us to help structure its CSR diagnostic and financial management. It hesitated between an in-house carbon assessment (free, unreliable) and a full diagnostic (€15,000). We presented Diag Décarbon'Action: for €6,000, it obtained a professional, comprehensive audit, verifiable with its customers. Within six months, the investment proved strategic: it identified energy reduction opportunities that generated €30,000 in annual savings.

That is the real differentiator. A carbon assessment is not a cost to minimize; it is a tool for cost control and competitiveness. Public subsidies exist precisely to democratize this approach. Failing to take advantage of Diag Décarbon'Action when you qualify means leaving €4,000 in public support on the table.

Hayot Expertise advice. If you have fewer than 500 employees and no carbon assessment in the past 5 years, apply for Diag Décarbon'Action without delay. The process takes 30 minutes and you receive a decision in 2-4 weeks. Make use of a €4,000 subsidy for a diagnostic you will eventually need to do (customer demand, bank requirement, future regulation). In parallel, prepare to integrate your carbon assessment into your financial management reporting: that is where economic impact materializes.