Data centre waste heat and Germany's Energy Efficiency Act

Germany's Energy Efficiency Act (Energieeffizienzgesetz, EnEfG) of 13 November 2023 contains rules written specifically for data centres. They cover the efficiency of the infrastructure, the reuse of waste heat, the sourcing of electricity, energy management and the publication of operating data. Every figure in this article is taken from the statute as published on gesetze-im-internet.de, with the section cited.

Which data centres does the Energy Efficiency Act apply to?

All with a non-redundant rated electrical connection capacity of 300 kilowatts or more (§ 3 no. 24 EnEfG).

Covered are structures for housing, connecting and operating IT and network equipment, together with the systems for power distribution, cooling, resilience and security. Pure network nodes that mostly do not process data are excluded (§ 3 no. 24 letter c). The operator is whoever owns the data centre or the colocation space, or holds comparable rights of use (§ 3 no. 3). Anyone running IT of 50 kilowatts or more inside someone else's data centre has obligations of their own as an operator of information technology (§ 3 no. 4).

What level of energy efficiency does the Act require?

New data centres must reach a power usage effectiveness of no more than 1.2; existing ones 1.5 and later 1.3 (§ 11(1) and (2) EnEfG).

The statute's term is Energieverbrauchseffektivität, the PUE: the ratio of the annual energy demand of the whole data centre to that of the IT, under DIN EN 50600-4-2 (§ 3 no. 15). A value of 1.2 means that for every kilowatt-hour in the servers, at most 0.2 kilowatt-hours may go to cooling, power distribution and auxiliary systems.

• Operation before 1 July 2026: no more than 1.5 from 1 July 2027 and no more than 1.3 from 1 July 2030, as an annual average and permanently (§ 11(1)).
• Operation from 1 July 2026: no more than 1.2, reached as an annual average no later than two years after commissioning and maintained permanently (§ 11(2) sentence 1 no. 1 and sentence 2).

Electricity used by equipment that serves solely to upgrade the waste heat, such as heat pumps for a heating network, is left out of the calculation (§ 11(2) sentence 3). Using waste heat does not worsen the metric.

How much waste heat must a new data centre reuse?

At least 10 percent reused energy for operation starting from 1 July 2026, 15 percent from 1 July 2027 and 20 percent from 1 July 2028 (§ 11(2) sentence 1 no. 2 EnEfG).

The share is measured as the energy reuse factor under DIN EN 50600-4-6, and it too must be reached as an annual average no later than two years after commissioning (§ 11(2) sentence 2). For data centres that began operation before 1 July 2026, § 11 sets no quota; they fall under the general duty in § 16 to avoid and use waste heat as far as possible and reasonable (§ 11(4)).

The Act acknowledges that a data centre cannot dispose of its heat alone. § 11(3) names three cases in which the quota does not apply:

1. The share falls after commissioning through events for which the operator is not responsible (no. 1).
2. A nearby municipality or heating network operator declares, in an agreement with the operator, a concrete intention to build or permit a heating network, so that the quota can be met within ten years. The agreement must cover an investment plan, the cost of the connecting pipeline and the price of the heat (no. 2).
3. A nearby heating network operator does not accept an offer of the heat at cost within six months, although the operator has the infrastructure ready, in particular a heat transfer station (no. 3).

The second case is the one that counts for new sites: an agreement on a heating network that does not yet exist satisfies the Act, provided both sides talk in the site phase rather than after the building application.

What other obligations apply to data centres?

Renewable electricity, an energy or environmental management system, annual data for a register and disclosure of waste heat (§§ 11 to 14 and 17 EnEfG).

• Renewable electricity. On a balance-sheet basis, 50 percent from 1 January 2024 and 100 percent from 1 January 2027 (§ 11(5)).
• Energy or environmental management system. To be set up by 1 July 2025, with continuous measurement and measures for ongoing improvement (§ 12(1) and (2)). From 1 January 2026 it must be validated or certified for data centres of 1 megawatt or more of non-redundant rated capacity, and from 300 kilowatts for public-sector data centres (§ 12(3)). Exempt is a data centre that delivers at least 50 percent of its reused energy through a heating network and consumes no more than 7.5 gigawatt-hours of final energy on a three-year average (§ 12(4)).
• Reporting and register. By 31 March each year, operators publish data on the previous year in line with Annex 3 and submit it to the federal government (§ 13(1)): among other things connection capacities, total electricity consumption, share of renewables, quantity and temperature of waste heat released and delivered, PUE and energy reuse factor. The federal government keeps the data in the Energy Efficiency Register for Data Centres and transfers it to a European database (§ 14).
• Waste heat platform. Like other companies, data centres disclose the quantity, output, load profile and temperature level of their waste heat to heating network operators on request and report these details by 31 March each year to the Bundesstelle für Energieeffizienz, the federal energy efficiency office (§ 17(1) and (2)).

What can data centre waste heat do for a municipality?

Provide a heat source that is available all year, predictable and needs no fuel.

A data centre converts almost all of its electricity into heat, evenly, day and night, summer and winter. For a heating network that is base load.

The constraint is temperature. Air-cooled data centres release heat at a low level, below what a conventional district heating network carries. Then heat pumps are needed, whose electricity does not count towards the PUE, or a network designed for low temperatures, such as local heating networks for new housing. Liquid-cooled systems, increasingly used for dense computing loads, deliver higher temperatures.

Offtakers are heating networks, residential quarters, public buildings, swimming pools, greenhouses and businesses with low-temperature process heat demand. Where a municipality draws up its heat plan, a data centre belongs in it as a source. Under Germany's Heat Planning Act, heat plans must be in place by 30 June 2026 for municipal areas with more than 100,000 inhabitants and by 30 June 2028 for all others (§ 4(2) WPG). Where site decision and heat planning coincide, both sides gain.

What does this mean for site selection and planning?

Heat offtakers are a site criterion, and the conversation with the municipality starts in the site phase.

The obligations of the EnEfG cannot be retrofitted without becoming expensive. A PUE of 1.2 requires cooling designed for it from the outset. A reused energy share of 10, 15 or 20 percent needs an offtaker who is there at commissioning or within the agreed period. Both are decided before the land is bought.

Bright & Green develops, builds and operates data centres and battery storage and comes from the energy side. We plan waste heat, grid connection and generation as one system, and we open the conversation with the municipality early. More on the pages for municipalities and energy and grid.

Note: This article reflects the text of the EnEfG of 13 November 2023 as published on gesetze-im-internet.de. It is not legal advice. Check the version in force before taking decisions.

Frequently asked questions

Does the Energy Efficiency Act also apply to existing data centres?

Yes. They must meet a PUE of 1.5 from 1 July 2027 and 1.3 from 1 July 2030 (§ 11(1) EnEfG), the renewable electricity requirement (§ 11(5)), the management system (§ 12) and the reporting duty (§ 13). § 11 sets no reuse quota for them; § 16 requires waste heat to be used as far as possible and reasonable.

What happens if there is no heat offtaker?

Then § 11(3) EnEfG applies: an agreement with a municipality or heating network operator on a network yet to be built, an offer at cost that is not accepted within six months, or a decline through no fault of the operator. The burden of proof lies with the operator.

Must a data centre give its waste heat away for free?

The Act sets no price. § 11(3) no. 3 EnEfG refers to an offer at cost, and no. 2 requires an agreement with the municipality to settle the price. The price is a matter of negotiation.

Where is the register data published?

Operators publish their Annex 3 data themselves and submit it to the federal government (§ 13(1) EnEfG). The federal government consolidates it in the Energy Efficiency Register for Data Centres and transfers it to a European database (§ 14).