Is ISO 50001 mandatory? What the 2.75 and 23.6 GWh thresholds really mean

For ten years the French rule on energy audits was easy to state: large companies had to audit, others did not. The criterion was size — headcount, turnover, balance sheet. That is no longer the case. Since 1 October 2025 the energy code (code de l’énergie) works on consumption, and two thresholds expressed in gigawatt-hours decide what you must do.

The change is worth understanding precisely, because it brings in companies that were previously outside the scope — an energy-intensive SME manufacturer, an operator of several logistics sites — and takes others out.

What changed, and why

Law no. 2025-391 of 30 April 2025, known as the DDADUE law, transposed the European energy efficiency directive into French law. It rewrote articles L. 233-1 and following of the energy code, and those provisions came into force on 1 October 2025.

The logic of the directive is coherent: a company’s energy stake is not determined by its size but by what it consumes. A 500-employee consultancy uses less energy than a 40-person foundry. The new criterion corrects that anomaly.

The two thresholds and what they trigger

The regime distinguishes two levels of average annual final energy consumption, assessed over the last three financial years.

Average annual consumption	Obligation
Below 2.75 GWh	No obligation under these articles
From 2.75 GWh	Energy audit every four years, meeting the general requirements of standard NF EN 16247-1, unless an energy management system is in place
From 23.6 GWh	Certified energy management system

The upper threshold of 23.6 GWh corresponds to the 85 terajoules set by the European directive; the lower one to 10 terajoules. These are therefore European orders of magnitude transposed, not nationally negotiated figures.

Two deadlines come with the scheme, aligned on the directive’s timetable: 11 October 2026 for the first energy audit of companies caught by the lower threshold, and 11 October 2027 for putting in place the certified energy management system required above the upper threshold.

How the audit and the management system interact

This is the point most often missed. The two obligations do not stack: a company that operates an energy management system is not required to carry out the periodic energy audit.

In other words, between 2.75 and 23.6 GWh you choose between two compliance routes:

• the audit route: a one-off engagement, renewed every four years, carried out under standard NF EN 16247-1;
• the management-system route: a permanent framework, structured by ISO 50001, which removes the audit requirement.

That choice is not neutral and deserves to be weighed against your energy bill, your consumption trajectory and your other obligations. We compare them in ISO 50001 or an NF EN 16247 energy audit.

Above 23.6 GWh there is no longer a choice: the certified management system is the obligation.

What must be reported to the authorities

The obligation does not stop at doing the work. Companies concerned must send the administrative authority, electronically, the information relating to how they meet their obligations, within two months of either certifying their energy management system or completing the audit.

A certified company is therefore exempt from auditing, not from reporting. The distinction is worth noting, because it is a recurring oversight.

Penalties

The energy code sets out a two-stage procedure. The administrative authority first serves formal notice on the company to comply within a period it sets, and may make that notice public. If the company does not comply within the period, a fine may be imposed, proportionate to the seriousness of the breach, the party’s situation, the extent of the harm and the advantages gained — capped at 2% of the pre-tax turnover of the last closed financial year, raised to 4% for a repeat breach of the same obligation.

Publication of the formal notice is not the least dissuasive part for a company subject to non-financial reporting requirements or bidding for public contracts.

What research says about turning obligation into effect

A regulatory obligation does not mechanically produce savings: companies still have to implement what the audit recommends. That is precisely what Lisa Nabitz and Simon Hirzel examined in a study published in 2019 in Energy Policy, devoted to how the mandatory energy audit obligation was transposed across the then twenty-eight EU member states. They document wide heterogeneity in national transpositions — adjusted scopes, diverging definitions of the companies covered — which makes cross-country comparison of effects difficult (see the study).

Moving to a consumption criterion common to the whole Union answers that criticism directly: it narrows the room for national interpretation of who is covered.

On effects, a study by Patrick Fitzgerald, Peter Therkelsen, Paul Shaeffer and Prakash Rao published in 2023 in Sustainable Energy Technologies and Assessments measures, across 83 ISO 50001-certified industrial sites, an annual energy performance improvement of around 4.1% in the first year and still around 3.4% twelve years after implementation (see the study). The case for the management-system route is not only regulatory: it is the persistence of the gain that sets it apart from a one-off audit.

The calculation to run now

It comes down to an addition. Take twelve months of invoices for every energy you buy — electricity, gas, heat network, heating oil, fuels, vehicle fuel — convert everything to kWh, add it up, then repeat over the last three financial years and take the average.

Three cases emerge:

• below 2.75 GWh: nothing to do under these articles; a voluntary approach obviously remains open if your bill justifies it;
• between 2.75 and 23.6 GWh: weigh the periodic audit against a management system, remembering that the latter removes the former;
• above 23.6 GWh: start building the certified energy management system, bearing in mind that a full cycle — energy review, indicators, internal audit, management review, two-stage initial audit — needs several months of real operation before it can be audited.

A company close to the lower threshold should redo this calculation every year: a rise in activity, a process change or an electrified vehicle fleet can push it over without anyone noticing.

Going further

The certification journey is described in our guide to setting up an ISO 50001 energy management system, and the comparison with the environmental standard in ISO 50001 and ISO 14001: two standards, two logics. If you are looking for a provider for the audit route, our article on OPQIBI qualifications 1905 and 1911 explains how to check their competence.

Take action

Run the addition first: your average consumption in GWh over three financial years alone determines your regime, and no one but you has the invoices to calculate it. Depending on the result, choose between audit and management system — and keep in mind that the 11 October 2027 deadline leaves less room than it seems for a system still to be built. The full scheme sheet, with the steps and frequently asked questions, is here: ISO 50001 certification.