Series "The data center through an investor's eyes" · Stranded asset · Article 9 · PUE and value · Retrofit
New AI campuses get the headlines. Less is said about the data centers already running in France, many of them designed in the 2000s and 2010s for air-cooled racks of 5 to 10 kW. These sites will have to upgrade, under pressure from regulation and from tenants. It is a large undertaking, and for investors as much an opportunity as a risk.
WHY NOW
The average PUE of French colocation data centers is improving: 1.51 in 2022, 1.42 in 2024 according to Arcep. But the average hides wide gaps between recent and older sites. Several pressures are arriving at once:
| Pressure | What it changes |
|---|---|
| EU rating scheme | Proposed on 21 September 2026 for sites above 500 kW, first labels expected in 2027. Consultation open on minimum performance standards. |
| Annual reporting | Sites above 500 kW already report their indicators to an EU database. Gaps become visible. |
| Waste heat | The Energy Efficiency Directive requires data centers above 1 MW to reuse their waste heat unless shown not technically or economically feasible. |
| F-gases | The 2024 EU regulation phases down HFCs. Older chillers become more expensive to maintain and recharge. |
| French tertiary decree | Energy reduction targets (−40% by 2030) for covered floor areas, with specific rules for data centers. |
| French BACS decree | Building automation and control required above 290 kW of heating or cooling capacity. |
| Tax | The reduced electricity excise rate for data centers is subject to environmental conditions. |
| Tenants | Demand for AI density, ESG requirements from large customers in tenders. |
FOUR LEVELS OF RETROFIT
1. Optimisation without major works
Hot or cold aisle containment, higher set-point temperatures, fan tuning, monitoring and sub-metering. Fast, cheap, and often enough to gain a few tenths of PUE. It is also the foundation of the European Code of Conduct.
2. Replacing technical equipment
Chillers with lower-impact refrigerants, free cooling, higher-efficiency UPS, variable-speed drives. These works follow the normal equipment renewal cycle, but must be carried out on a live site without service interruption.
3. Partial AI conversion
Fitting a hall with liquid cooling, strengthening power distribution and checking the structure for heavier racks. This is where the site's future competitiveness is decided, as explained in How to avoid a stranded asset.
4. More power
Often the real bottleneck. Increasing connected power means an application to Enedis or RTE, sometimes new transformers, with lead times in months or years.
WHAT IT MEANS FOR AN INVESTOR
An older site that already has a secured grid connection holds what new projects lack most: available power without years of waiting. Buying and upgrading it can be faster than a new build. It is a classic value-add strategy, provided three things are assessed properly:
Condition and age of technical equipment, refrigerants, end of life
Structure: floor loading, height, space for new plant
Feasibility of works on a live site, and risk to existing tenants
Permits: classified installations, planning, tertiary decree
Total retrofit cost compared with a new build in the same market
Conversely, an older site that does not upgrade will see its rating slip, tenants move to newer sites and its value fall. For these assets retrofit is not optional: it is a question of timing.
WHO TO BRING IN
A successful retrofit needs skills rarely found together: energy and mechanical engineering for technical packages and compliance (tertiary decree, BACS, energy audits), high-voltage expertise for grid connection and distribution, and coordination that respects live operations. The GridReadiness network brings these profiles together, for example Geoffrey Garriga for energy compliance and mechanical packages, and Xavier Watrelos for grid connection and industrial projects. See also PUE and data center value.
Sources: Arcep annual survey on sustainable digital (2026, 2024 data); Energy Efficiency Directive (EU) 2023/1791, Article 26; F-gas Regulation (EU) 2024/573; European Commission, 21 September 2026; French BACS decree; French tertiary decree. This article is not legal advice.
FREQUENTLY ASKED QUESTIONS
Why upgrade an existing data center?
To stay compliant with tightening rules (EU rating, F-gases, waste heat, French tertiary and BACS decrees), cut energy costs and meet AI tenants' density needs.
Can an existing data center host AI?
In part, if connected power allows, the structure can carry heavier racks and a hall can be fitted with liquid cooling.
Is a retrofit faster than a new build?
Often, when the site already has enough connected power, because grid capacity drives the longest lead times for a new project.