Energy audit or ISO 50001: what must your company do?

Most small and medium businesses in Belgium fall below every threshold. Larger sites need an energy audit or an energy plan, drawn up by an approved expert. The very largest will need a certified ISO 50001 system from 11 October 2027. Every one of these obligations starts with measured data. Our energy management system gives you that data per phase and per minute. A business battery comes later, when the measurements show which peaks and solar surplus are left.

Maybe this is your situation. A newsletter from your sector federation says new energy rules are coming "from 10 TJ". Your finance director asks one question: does this apply to us? The last energy report is somewhere in a drawer, full of PJ, TJ and internal rates of return. And a battery supplier has just told you that a battery "counts as an energy measure".

That confusion costs more than it seems. A missed deadline can block subsidies: in Wallonia, a large company without its audit loses access to regional aid. An audit built on estimates recommends a heat pump or electric vans without checking the connection. And a battery bought "for the audit" does not lower your energy use at all.

The numbers are usually less scary than the units. A site in Beveren uses 350,000 kWh a year, which feels like a lot. That is about 1.3 TJ, far below the new European audit threshold of 10 TJ. What such a site does need is the same thing every audit asks for: real measurements. For a landscaping contractor in Zele, we first monitored the warehouse, offices and house for a month, before any sizing.

Which energy obligations apply to companies in Belgium?

Three layers apply at once: the European Energy Efficiency Directive, the rules of your region, and voluntary agreements for energy-intensive sites. The directive sets the minimum. The regions decide who does what, who carries out the audit and what must be implemented.

Flanders also asks for an energy study with some permit applications. That applies to a new site using at least 0.1 PJ, or a change that adds at least 10 TJ a year. Since 1 January 2026, large non-residential buildings in Flanders need an EPC NR certificate. A valid EPC NR can exempt those buildings from the audit or plan.

How do you know whether your company crosses 10 TJ?

Add up all the energy your site uses in a year, in every form, and convert it to kWh. Electricity, natural gas, fuel oil and other fuels all count. The European rule looks at the average of the last three years.

One terajoule is about 278,000 kWh. That makes the thresholds easier to picture:

Gas usually decides it, not electricity. A bakery, a greenhouse or a food processor with gas heating crosses 2.8 GWh much sooner than an office. Take your supplier invoices for gas and electricity, add fuel for your own vehicles and machines, and you have your first answer.

Energy balance, energy audit or energy plan in Flanders: what is the difference?

All three are reports by an approved energy expert that list energy-saving measures, but the depth and the duty to act differ. VEKA, the Flemish energy and climate agency, manages them through the web application "Energierapport ondernemingen".

• Energy balance (0.02 to 0.05 PJ): a simpler overview. You carry out the no-regret measures for your sector, with a payback of at most three years, within four years.
• Energy audit (0.05 to 0.1 PJ, and large companies below 0.1 PJ): based on current, measured and traceable data, including the load profiles for electricity. Every measure with an internal rate of return of at least 13% after tax must be done within three years. The audit is valid for four years.
• Energy plan (from 0.1 PJ): the same 13% rule, but VEKA must declare the plan compliant. You enter the results within three months of that declaration.

Energy-intensive sites could also join a voluntary energy policy agreement (EBO). The current round runs from 2023 to 2026.

That phrase in the audit rules matters: measured load profiles for electricity. An auditor who only has your yearly invoices can only estimate. Quarter-hour data from your digital meter, or a sub-meter on the big machines, shows when the energy is used. That is also the data that later decides whether a battery makes sense.

What changes for Flemish companies in 2027?

Flanders is moving to the thresholds of the new European directive, based on energy use per establishment. The Flemish government approved the texts in principle on 17 July 2026. According to Voka, they are not final yet.

From 10 TJ, the draft also asks for yearly data to VEKA. That covers energy use per carrier, purchased and delivered quantities, and your own electricity production. For sites from 85 TJ, a new voluntary agreement (EBO3, 2027-2030) is in preparation, with an 11% threshold instead of 13%.

Behind this is the European directive. It requires an energy audit from 10 TJ, with a first audit by 11 October 2026 and then at least every four years. Companies must turn the audit into a concrete action plan. The plan and the share of recommendations carried out must appear in the annual report.

Which audit rules apply in Wallonia and Brussels, and what replaced the accords de branche?

In Wallonia, large companies must have an energy audit every four years; in Brussels, both large companies and large consumers. Both regions exempt companies that already work with ISO 50001.

Wallonia. The audit must be done by an auditor labelled under AMUREBA, the Walloon scheme for audits and studies. It covers at least 80% of the final energy use in Wallonia: processes, buildings, own energy production and internal transport. Companies in a sector agreement are exempt. A company that misses the obligation loses access to regional aid and risks financial sanctions.

The sector agreements themselves have changed. The accords de branche ran from 2003 to 2023 in two generations. Since 1 April 2024, conventions carbone replace them. They run for eight years and are open to groups of companies above 50,000 tonnes CO2-eq or 150 GWh of energy use. Measures with more than 11% internal rate of return count as firm commitments. In return, members get a reduced green-certificate quota on their electricity bill.

Brussels. A large company must have an audit done by an auditor approved by Bruxelles Environnement and renew it every four years. Large consumers need an audit when they apply for or renew an environmental permit. Examples are offices from 3,500 m² or shops from 1,000 m². The permit then sets energy-saving targets based on the audit.

For grid tariffs and peaks in these two regions, read our article on grid tariffs for businesses in Wallonia and Brussels.

Is ISO 50001 mandatory, and is it the same as energy management software?

ISO 50001 is a voluntary international standard for how an organisation manages energy. It is not a device or an app. It becomes mandatory only above 85 TJ, and then it must be certified by an independent body.

An ISO 50001 system sets an energy policy and a baseline of your use. It identifies the processes that use the most energy and follows them with performance indicators. It plans actions and improves them every year. A certificate stays valid for three years, with a surveillance audit every year.

Two things are easy to confuse:

• ISO 50001 = the method: who is responsible, which targets, how you check progress.
• Energy management software (EMS) = the tool: it measures, and with a battery it steers loads automatically. Our article on what an energy management system does for a business explains the tool.

The tool supports the method. ISO 50001 asks for better measurement and reporting of your energy use. Our monitoring software shows use per phase, reports per minute, hour or day, and lets you look back at one exact moment. That is the raw material for a baseline and for indicators.

Where does a battery fit in an energy audit or energy plan?

A battery does not lower how much energy your site uses. It moves energy in time, and every charge and discharge loses a little. So a battery on its own is rarely an energy-saving measure in an audit. It fits in three other places.

• Next to solar power: a battery stores daytime surplus for the evening, so you buy less energy from the grid. How that is counted in your audit is a question for your energy expert. Our article on business solar panels covers the solar side.
• With electrification measures: audits often recommend replacing gas with a heat pump, or fuel with electric vehicles. That raises your electricity peak. A battery can cover that peak when the connection is too small. See our articles on a heat pump in a business and chargers without a heavier connection.
• Against peak costs: in Flanders, your highest quarter-hour of the month drives the capacity tariff. That is a cost, not energy use, so it sits outside the savings rules. Read how the capacity tariff for businesses works.

How do measurements turn an audit into a better battery decision?

The same measurements serve both: the auditor sees where energy goes, and you see when it is used. That avoids paying twice for data.

1. Step 1: Collect a year of quarter-hour data. Download it from your grid operator portal, or measure for a few weeks where data is missing.
2. Step 2: Give the same data to your energy expert. The audit then works with measured profiles instead of estimates.
3. Step 3: List the electrification measures from the audit, with their power in kW and when they will run.
4. Step 4: Check your peak and your connection with those new loads added. Only then do you size a battery, on what remains.

Our article on peak demand in a business explains how one quarter-hour sets your bill. For support, the tax deduction and subsidies for a business battery are listed in a separate article.

When is a battery not the answer to your audit?

When your energy use is mainly heat and your peak is low, a battery changes little. Insulation, heat recovery, a better compressor or LED lighting then come first.

• Most of your energy is gas: the savings are in heat, not in electricity storage.
• No solar surplus and a flat load: there is little to move in time.
• Your connection has room: a heavier connection may cost less than storage.

What happens when you ask us about your energy data and a battery?

We start with your data, not with a device. The legal audit or energy plan itself is drawn up by an approved expert in your region.

1. Step 1: Analysis and sizing. We read your quarter-hour data and your plans for heat pumps, chargers or machines. Where data is missing, we measure first.
2. Step 2: Technical design. We check whether a battery, load control or both fit your peaks and solar production.
3. Step 3: Installation and commissioning.
4. Step 4: Monitoring and support. With our business batteries, monitoring, control and optimisation are included, so the data for your next audit keeps coming in. How a project runs from start to finish is in our step-by-step plan for a business battery.