EU Directive 2023/1791 on energy efficiency

Directive (EU) 2023/1791, the recast Energy Efficiency Directive (EED), repealed Directive 2012/27/EU with effect from 12 October 2025. The 2012 Directive required an energy audit from every enterprise that was not an SME. The recast replaces that size test with an energy test, so a mid-sized manufacturer that was exempt may now have a deadline, and a large company that uses little energy may not. The duties reach enterprises through national law, so the dates below are the EU minimum.

Duties for enterprises (Article 11)

Both thresholds apply to the average annual final energy consumption over the previous three years, for all energy carriers together. The Commission's guidance on Article 11, Recommendation (EU) 2024/2002, reads this as years n-3, n-2 and n-1. The obligation for 2025 therefore rests on the figures for 2022, 2023 and 2024.

Qualified or accredited experts must carry out the audit independently, under the qualification schemes of Article 28. The alternative is an audit implemented and supervised by an independent authority under national law. An enterprise that already audits under the 2012 rules continues on its four-year cycle. A large enterprise below 10 TJ no longer has a mandatory audit. An SME above 10 TJ now has one.

Article 11 has two exemptions. Paragraph 10 exempts an enterprise with an energy performance contract that covers the necessary elements of an energy management system and meets Annex XV. The Commission's guidance says that such a contract must cover every site and every energy-consuming process, and calls the case "hardly imaginable". Paragraph 11 exempts an enterprise with a certified environmental management system, such as ISO 14001 or EMAS, if that system includes an energy audit to the Annex VI criteria.

Under Article 11(3), an enterprise above either threshold in a given year must make that information available to the national authority. Article 32 leaves the penalties to each Member State.

An audited enterprise must draw up an action plan from the audit recommendations. The plan identifies measures to implement each recommendation, where that is technically or economically feasible, and goes to the enterprise's management. The Member State must ensure that the plan and the recommendation implementation rate are published in the enterprise's annual report and made publicly available. Trade secrets and confidential information are protected. This duty is in Article 11(2), so it applies to audited enterprises, not to enterprises with a certified energy management system.

The Directive does not define the implementation rate. The simplest figure to defend is the number of recommendations implemented divided by the number made: 5 of 12 is 42%. The rate says nothing about energy, so report the measured saving of each implemented measure against the audit baseline next to it. The savings guide explains how to measure one.

National law can go further than the Directive. In Germany, the Energieeffizienzgesetz (EnEfG) requires an energy or environmental management system above 7.5 GWh a year (§ 8). It also requires published implementation plans for economic measures above 2.5 GWh a year (§ 9), A measure counts as economic when its net present value, calculated to DIN EN 17463, turns positive within half of its useful life. Measures with a useful life above 15 years are not counted.

Working out which threshold applies

1 kWh is 3.6 MJ, so 1 TJ is 277.8 MWh. The 10 TJ threshold is 2,778 MWh a year and the 85 TJ threshold is 23,611 MWh. The Commission's guidance bases the test on invoiced energy, plus renewable energy produced and used on site, such as PV. PV exported to the grid is subtracted. Energy that an energy service provider delivers, such as heat under a supply contract, counts for the enterprise that buys it. The energy unit converter and the gas m³ to kWh calculator put different fuels on one scale.

As an example, take a food manufacturer with one plant and a delivery fleet. Diesel is converted at 36 MJ per litre: the net calorific value for gas/diesel oil in Regulation (EU) 2018/2066 is 43.0 MJ/kg, and a litre weighs about 0.84 kg. The gas figures are on the same net basis.

The three-year average is 10.88 TJ, so the enterprise must be audited, although 2024 alone was below 10 TJ. Without the diesel, the average is 8.90 TJ, and the enterprise would conclude, wrongly, that it is out of scope.

These errors put an enterprise in the wrong band:

• Transport fuel is left out. Fuel cards and fleet invoices often go to a different budget holder from the utility bills.
• One year is used instead of the three-year average.
• Linked enterprises are left out. The guidance adds the consumption of each linked enterprise (more than 50% control) anywhere in the EU, following the SME definition in Recommendation 2003/361/EC. Partner enterprises are not added.
• Bills are estimated. An actual read corrects the estimates before it, so a year's total can move by the size of the correction. Use actual reads at the year boundaries, and compare billed reads with the meter register.
• Gas is on a different basis from the other carriers. Gas is usually invoiced in kWh on gross calorific value, which for natural gas is about 11% above net. Use one basis for all carriers, and record which one.
• The building is rented. The guidance leaves it to Member States to say who audits a building that one party owns and another operates.

What an audit must contain

Annex VI sets the minimum criteria for every Article 11 audit, including an audit done inside a management system. The audit must:

• use up-to-date, measured, traceable operational data on energy consumption and, for electricity, load profiles;
• review in detail the consumption profile of the buildings, industrial operations and installations, including transport;
• identify energy efficiency measures, and the potential for cost-effective use or production of renewable energy;
• use life-cycle cost analysis instead of simple payback wherever possible;
• be proportionate, and representative enough to give a reliable picture of overall energy performance.

The audit data must be storable for historical analysis and for tracking performance. The European audit standard is the EN 16247 series: part 1 general requirements, part 2 buildings, part 3 processes, part 4 transport and part 5 auditor competence.

The Directive does not say how much of the consumption an audit must cover. The Commission's guidance reports national minimums of 65% to 90% of total consumption. One approach audits every area above 10% of consumption, to reach at least 80% in total. For an enterprise with many similar sites, the guidance suggests a sample of at least the square root of the number of sites: for 25 similar shops, audit at least 5.

Other parts of the Directive

Article 36 set 11 October 2025 as the transposition deadline for Articles 1 to 11 (except one subparagraph of Article 4) and for most of Articles 21 to 32. The data centre reporting in Article 12(1) started earlier, on 15 May 2024. The metering and billing Articles 13 to 20 apply from 12 October 2025.

What the duties mean for data

Annex VI(a) decides the metering. It asks for measured, traceable operational data and, for electricity, load profiles. A monthly bill gives neither: it is one number a month, and it can be an estimate. The supplier's interval data (half-hourly or 15-minute, depending on the market) gives the load profile of the site, but not how the load divides between uses.

An energy management system needs the same data in more detail. ISO 50001:2018 requires an energy review that identifies the significant energy uses (clause 6.3), energy performance indicators (6.4), an energy baseline (6.5) and a plan for the collection of energy data (6.6). Submeters on the significant energy uses supply the consumption of each use, the energy side of each indicator, such as kWh per tonne of product, and the baseline against which each action-plan measure is measured.

Each month, compare the sum of the submeters with the main meter. The difference is the unmetered load. If it changes without a known cause, look for an unmetered board, a current transformer on the wrong phase, or a current transformer fitted in reverse. The submetering guide explains how to choose the points, and the ISO 50001 guide explains what a certified system requires.

Metering for the EED with EpiSensor

ZEM electricity monitors meter the significant electricity uses. They report over the Zigbee mesh, so they are installed without data cables. ZPC pulse counters read the pulse outputs of gas, water and heat meters. ZHM M-Bus interfaces read heat and other M-Bus meters, and ZIO analogue sensors read 4-20 mA process signals, such as a production flowmeter for an indicator. A Gateway running Edge records the interval history on site. The energy manager or auditor can export any selection of it to CSV from the Edge Data page. Edge can also send the data over MQTTS or HTTPS to an energy management platform, where the site uses one.