The problem. The sale file says the factory "has 10 MW". The transformer is still in the yard. But a future data center operator does not want to know what the factory used to draw: it wants to know how many racks it can power, and from when. In between sit connection rules, a grid operator and often works. A brownfield saves time only if its power is still there.
10 MVA, 10 MW OR 7 MW OF IT?
The former factory's peak (e.g. 10 MW): what it drew at one point, often with a profile very different from a data center running continuously
IT load: what is left for servers. With 10 MW confirmed continuously and a PUE of 1.30, about 7.7 MW remains, to be checked on the hottest day and with one item in maintenance
WHAT HAPPENS TO AN IDLE SITE'S CAPACITY
Since 1 August 2025, at both RTE and Enedis, the connection capacity of a site connected for at least five years is reset each year to 125% of the maximum it actually drew over the previous five years, without exceeding its current capacity. A factory that slows down, then stops, therefore sees its connection capacity shrink year after year. Access contracts may also be terminated and assets removed or reassigned.
In practice, the older the shutdown, the less the historical megawatts are guaranteed. Only a written answer from the grid operator says what can still be used.
DOCUMENTS TO GATHER, IDEALLY BEFORE CLOSURE
Grid access contracts and subscribed capacity
Consumption records for recent years, especially peaks
Specifications and condition of the substation and transformers
Written authorisation for the buyer to approach the grid operator
THE ANSWER TO GET FROM THE GRID OPERATOR
A written, costed answer: capacity available for the new use, the date it is available, any limitations, works required and their cost. If the operator confirms 4 MW out of 10, those 4 MW carry value in the price; the other 6 remain an extension hypothesis.
COSTS A SITE VISIT DOES NOT SHOW
Soil remediation under the future substation, asbestos in the roof, demolition, permits, extending a power line, bringing in fibre: these can absorb the time saved. In Marseille, the MRS5 project on a former sugar silo required demolishing the silo and extending a 20 kV underground line from an existing substation, according to the environmental authority's opinion.
FROM 1 TO 20 MW, DIFFERENT MARKETS
At 1 or 2 MW, the question is local: a regional host, a company or a local authority looking for a second site. Between 3 and 8 MW, a colocation hall can open with a first customer, then grow. Between 10 and 20 MW, a high-performance computing customer may take most of the site, with cooling needs the hall cannot always meet. These projects often connect to Enedis's grid: see Enedis connection.
WHAT WE DO
For an industrial owner closing or selling, a buyer or a local authority with a brownfield: we review connection documents, prepare questions for the grid operator, assess what announced megawatts are really worth for a data center, and list conversion costs to quantify. See selling or leasing land to a data center.
Who is involved. Xavier Watrelos, a high-voltage engineer who has led industrial grid connections, with a land and planning expert from our network. Our commitment is a best-efforts obligation: only RTE and Enedis commit to capacity and a date.
Sources: CRE decision 2024-229 (annual 125% rule); Le Guide : Data Center, 2 November 2026, drawing on the DGE, Enedis, Cerema and the PACA environmental authority (in French).
FREQUENTLY ASKED QUESTIONS
Can a factory that had 10 MW host a 10 MW data center?
Not necessarily. A transformer nameplate and the factory's past peak guarantee neither today's available capacity nor IT load. A written confirmation from the grid operator is needed, then sizing with PUE and redundancy.
What happens to a closed factory's connection capacity?
Since August 2025, a site connected for at least five years has its connection capacity reset each year to 125% of its maximum draw over five years. An idle site therefore loses capacity over time, on top of contract terminations.