Heating cost allocation in your co-ownership: checking your share of heating, energy and water

The annual statement has arrived, and the heating or water line for your unit has grown considerably. Yet you turned the radiators down, or the apartment stood empty for part of the year. Before concluding that there is a mistake, you need to understand how that amount was calculated, because heating cost allocation in a co-ownership follows set rules.

In a building with a shared boiler room or a main water meter, the supplier sends a single bill to the owners' association (VME/ACP)GlossaryLegal entity that brings the co-owners together and whose sole purpose is the preservation and management of the building. It acquires legal personality as soon as a first unit is transferred, provided the deed of division and the co-ownership regulations have been transcribed. See the glossary. The syndic then allocates these heating and energy costs among the units, according to a rule they do not make up: it comes from the building's by-laws, and it often combines a flat-rate part and a measured part. In practice, your share therefore depends on three things: the key provided for, the measuring devices and, for water, the way Vivaqua or your water company bills the building. For an overall check of your statement, all items included, see the page on the annual service charge statement.

Who sets the allocation key for heating and energy costs?

The answer is in the by-laws. The Civil Code requires the co-ownership regulations to contain "the reasoned criteria and the method of calculating the allocation of charges" (article 3.85, § 1, para. 4, 2°, of the Civil Code). In older buildings, this key is often found in the deed of division (acte de base / basisakte)GlossaryNotarial deed that describes the building or group of buildings, its private and common parts, and sets the share of the common parts attached to each unit. Together with the co-ownership regulations, it forms the articles of the building and must be transcribed. See the glossary itself.

You will come across three situations.

1. With allocation by shares, heating and water follow the shares (quotités)GlossaryFraction of the common parts attached to each unit, set in the deed of division according to the respective value of the private parts. Shares determine the number of votes at the general meeting and can only be changed with the unanimous agreement of all co-owners. See the glossary of each unit, like the other common charges. It is simple, but the owner of a large, little-used apartment pays for their neighbour's consumption.
2. With allocation by consumption, each unit pays according to its readings. In its pure form this approach remains rare, because part of the heat cannot be measured in the dwellings.
3. With a mixed approach, a fixed part, allocated by shares or by heated floor area, covers boiler room losses, heating of the common parts and maintenance. A variable part follows the readings. The proportion between the two is written into the by-laws or into a meeting decision.

Our reading: in a building with collective heating, the mixed approach is the easiest to defend. It makes everyone pay for what they consume, without ignoring that part of the heat cannot be measured in the dwellings. That is also why an empty apartment keeps paying the fixed part.

Changing this key is not a formality. Changing the allocation of co-ownership charges is a matter for the general meeting, by a four-fifths majority of the votes (article 3.88, § 1, 2°, of the Civil Code). A co-owner who considers that the allocation causes them personal harm, or that the calculation is wrong, can also ask the court to correct it (article 3.92 of the Civil Code). This kind of claim is prepared with figures: readings over several years, plans, floor areas.

Heat meters and heat cost allocators: how each unit's consumption is measured

Two families of devices exist side by side in Belgian buildings.

The heat meter, or calorimeter, is fitted on the heating supply to an apartment. It measures the energy actually delivered, in kilowatt hours, using the water flow and the temperature difference between flow and return. It requires each dwelling to have its own heating loop, which is the case in many recent buildings.

The heat cost allocator is fixed to each radiator. It does not measure kilowatt hours but units, calculated from the radiator's temperature. These units are then corrected by coefficients that take account of the radiator's output and how it is installed. This is the solution for older buildings, where the heating riser passes through the apartments one after another.

The statement then works like this: the total cost of the year's heat is known (gas or heating oil bills, electricity for the boiler room, maintenance according to the by-laws). The fixed part is deducted and allocated according to the fixed key. The balance is divided by the total units or kilowatt hours read in the building, which gives a price per unit, then multiplied by the units for your unit.

Brussels pushes for individual metering; in Flanders, check the rules

In Brussels, Brussels Environment states on its page on EPB in co-ownerships:

“With collective heating, each dwelling must have a heat meter or an electronic heat cost allocator (calorimeter) in order to know the heat delivered.”

Brussels Environment, 'Co-ownership: what EPB requirements and obligations?'

If you live in Flanders, ask your syndic which metering obligations apply to your building, and check this with the Flemish Energy and Climate Agency (VEKA).

If your building has no measuring device at all, ask the syndic about bringing it into line and what that would cost. Installing devices is voted on at the general meeting, and the choice between buying and renting the devices deserves a comparison of several quotes.

Water: the Vivaqua bill in Brussels and your Flemish water company's bill

The principle is the same everywhere: with a collective meter, the water company knows only one customer. The sub-meters fitted in the apartments are private devices belonging to the co-ownership, read by the syndic or by an appointed company, not by the water company.

In Brussels with Vivaqua

Vivaqua's general terms and conditions define the collective meter as a "single meter for the building serving several dwellings". Where there are several users in a building served by such a meter, "only the subscriber is liable as debtor". Vivaqua also applies a fixed annual charge calculated according to the number of dwellings in the building, and it is Vivaqua that determines that number.

Since 2022, household consumption has been billed at a linear rate: a single price per cubic metre, whatever the number of people in the household. For 2026, vivaqua.be shows a fixed annual charge of 40.23 euros and a variable part of 5.35 euros per cubic metre, supply and sewerage included. Check these amounts on the water company's website for the year of your statement, as they are revised.

In practice: the fixed charge is logically allocated per dwelling, and the volume according to the sub-meters or the key in the by-laws. If the number of dwellings used by Vivaqua does not match the reality of the building (units merged, a shop converted), the syndic can report this to the water company.

In Flanders with your water company

In Flanders, the building is served by one of the drinking water companies of the Flemish Region, and the structure of the bill follows the tariff rules that apply there. Ask the syndic for the building's full bill, with the number of dwellings on which any fixed charge was calculated, and how that amount was allocated among the units.

In a building with a single meter, that allocation carries a lot of weight. An allocation purely per cubic metre, ignoring the fixed components of the bill, favours the heavy users. Check the rules for your building with your water company.

How do you check your share on the statement?

Work in this order, documents in hand.

A gap between the sum of the sub-meters and the main meter is normal up to a point: water for the common parts, cleaning, a leak or a private meter that under-reads. If it grows from one year to the next, look for a leak or a faulty device. The cost of this gap is often allocated by shares.

You have the right to access the non-private documents of the co-ownership, in the manner set by the house rules (ROI)GlossaryRules drawn up by private agreement that set out at least how the general meeting operates, how the syndic is appointed and the fortnight in which the ordinary general meeting is held. They are kept at the association's registered office and can be consulted free of charge. See the glossary or by the general meeting (article 3.89, § 5, of the Civil Code). Ask for the documents in writing, before the meeting that approves the accounts. If you stop paying while waiting for an answer, first read the page on the co-owner who does not pay: a dispute does not suspend the obligation to pay the advance payments.

To anticipate these amounts from one year to the next, the heating item deserves a detailed line in the annual budget. The general framework for charges is set out on the co-ownership service charges page.