> For the complete documentation index, see [llms.txt](https://help.immodio.app/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.immodio.app/en/anleitung/betriebskostenabrechnungen/heiz-und-warmwasserverbrauch/abrechnung-von-wg-mietverhaltnissen/todo-quadratmeter-und-zeitanteilig.md).
# Square metres and pro rata time (shared apartment rental)
This page explains when you can allocate heating and hot water consumption to the individual shared flat tenancies by square metres and pro rata time.
As a rule, billing is based on consumption. This requires suitable meters and meter readings for all relevant units. This variant corresponds to the standard case under the Heating Costs Ordinance and ensures that individual heating and hot water consumption is taken into account in the operating cost statement.
If, however, no usable consumption values are available for at least one unit, billing can instead be based on square metres and pro rata time.
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If you select the **"Square metres and pro rata time"** option, the heating and hot water costs are not allocated on the basis of individual meter readings.
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Instead, Immodio calculates the cost share of the individual units on the basis of the area stored in the [unit](/en/anleitung/immobilien.md#unit) and the respective period of use during the settlement period. This means that the actual consumption values of the individual units are not taken into account for the cost allocation, and that units with a larger area automatically bear a correspondingly higher share of the costs.
If there is a change of tenant during the settlement period, the period of use is taken into account pro rata by time.
#### A special feature of shared flat tenancies
With shared flat tenancies Immodio additionally takes into account which rooms in the shared flat are let under the respective tenancy. That is relevant above all where there were changes of tenant in individual rooms during the billing year.
For this Immodio automatically creates internal shared flat settlement periods. These periods are based on the respective start and end dates of the shared flat tenancies. With allocation by square metres you do **not** have to enter interim readings of the heating or hot water meters for these periods, unlike billing by meters and meter readings for a shared flat. Allocation is by area and time.
The cost share is first calculated for the unit and the respective period. Immodio then allocates this share to the shared flat tenancies concerned in proportion to the areas of the shared flat rooms let.
The finished operating cost statement for the shared flat tenancy additionally shows the key **"WG"**. It shows the share of the shared flat rooms let under the respective tenancy in the total area of the unit taken into account.
**Example 1: all rooms of the shared flat unit are let as shared flat rooms**
A shared flat unit has three rooms let:
* Room 1: 20 m²
* Room 2: 15 m²
* Room 3: 15 m²
In total 50 m² of shared flat room area is taken into account.
If room 1 is let under a tenancy, the share of that tenancy is:
20 m² of 50 m² = **40%**
This share is combined with the pro rata cost share of the shared flat unit.
**Example 2: only some of the rooms are let as shared flat rooms**
An apartment has three rooms. Only two of them are let as shared flat rooms:
* Room 1: 20 m²
* Room 2: 15 m²
* Room 3: 15 m², not let as a shared flat room
For the shared flat allocation Immodio only takes into account the rooms marked as let under a shared flat tenancy. The shared flat room area taken into account is therefore 35 m².
If room 1 is let under a tenancy, the share of that tenancy is:
20 m² of 35 m² = **57.14%**
In this case the third room is not allocated as a separate vacancy within the shared flat. It therefore does not increase the shared flat room area taken into account for the "WG" key.
{% hint style="info" %}
So that the shared flat allocation can be calculated correctly, all relevant [rooms](/en/anleitung/immobilien/einheit/grunddaten-einheit.md#raume) have to be created in the unit and given an area. Where room areas are missing, the statement for the shared flat unit concerned cannot be continued.
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#### When does this option make sense?
This option can make sense where consumption-based billing is not possible or not required in the specific case. That may be so, for example, where:
* there is a statutory exemption from consumption-based heating cost billing for the building,
* there are no suitable recording devices and the statement therefore cannot be prepared on the basis of actual consumption,
* several consumption values could not be recorded properly and no reliable consumption-based allocation is possible,
* the Heating Costs Ordinance does not apply, or applies only to a limited extent, to the specific building,
* or billing by consumption cannot be carried out for other legally recognised reasons.
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The reasons should be documented comprehensibly so that the statement can be checked and explained later.
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#### When should this option not be chosen?
Do not choose this option where complete and usable meter readings or consumption values are available for all units. In that case billing should generally be based on consumption.
If only individual meter readings are actually missing, you can first check whether the missing values can be substituted or estimated under the statutory rules, for example on the basis of earlier consumption values, comparable rooms or the average consumption.
### The tenant's right to a reduction
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Where heat or hot water costs are not billed by consumption contrary to Section 12 (1) of the Heating Costs Ordinance and there is no exception or special case, the tenant has the right to **reduce** the share attributable to them **by 15%**.
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The right to a reduction does not concern the entire operating cost statement, but the affected share of the heating or hot water costs that was not billed by consumption contrary to the Heating Costs Ordinance.
#### A. Special cases and exceptions
Billing by square metres can be appropriate where there is no obligation to bill by consumption in the specific case or where a statutory exception or special case applies.
It is important to note that the Heating Costs Ordinance generally assumes consumption-based billing. Billing entirely by floor area is therefore not the normal case but comes into consideration only in certain situations.
**This can be relevant in particular in the following cases:**
Buildings with no more than two apartments, one of which is occupied by the landlord
An important special rule concerns buildings with no more than two apartments, one of which is **occupied by the landlord themselves**.
In this case landlord and tenant can make arrangements that differ from the requirements of the Heating Costs Ordinance. It can be agreed, for example, that heating and hot water costs are allocated not by consumption but by living space or another comprehensible key.
**A typical example:**
A two-family house has two apartments. The landlord lives on the ground floor themselves, the apartment on the upper floor is let. The rental agreement provides that the heating costs are billed by living space.
The following is not sufficient, on the other hand:
* The building does have two apartments, but the landlord does not live in the house themselves.
* The building has three or more units (even though the landlord lives in the house).
* There is no clear contractual provision on the differing basis of billing.
**Important:** This special rule does not apply simply because a building is small. What matters is that there are at most two apartments and that the landlord occupies one of them.
Very low heating energy requirement
Under Section 11 of the Heating Costs Ordinance, certain provisions do not apply to rooms in buildings with a heating energy requirement of less than 15 kWh/(m²·a).
This concerns above all very energy-efficient buildings, in particular buildings meeting the passive house standard. In such buildings the influence of individual heating behaviour on the total costs is often considerably lower than in ordinary existing buildings.
**A typical example:**
A very well insulated apartment building meets, according to an energy certificate, a heating energy requirement of less than 15 kWh/(m²·a). An exception from consumption-based billing may therefore come into consideration for the heating costs.
**Important:** The low heating energy requirement should be demonstrable, for example by an energy requirement calculation, an energy performance certificate or corresponding planning documents.
Recording consumption or allocating costs is impossible or disproportionately expensive
An exception can apply where fitting recording devices, recording the heat consumption or allocating the costs would be impossible or possible only at disproportionately high cost.
Under the Heating Costs Ordinance, costs are disproportionately high where they cannot be recouped through savings that are normally achieved within ten years.
Typical cases can be:
* structural circumstances that make sensible recording impossible,
* technical peculiarities of the heating system,
* or exceptionally high costs for metering equipment and billing in relation to the savings that can be expected.
* Recording consumption would be possible only with considerable interference with the building fabric.
**Important:** This exception should be documented particularly carefully. You should if possible keep documents showing why recording consumption is impossible or economically disproportionate.
**Suitable evidence can be, for example:**
* a statement from a specialist company,
* quotations for metering equipment and conversion work,
* a technical description of the heating system,
* a calculation of the expected costs and savings,
* or a professional assessment by the metering service provider.
Older buildings from before 1 July 1981 where users cannot influence heat consumption
An exception can also apply to rooms that were ready for occupancy before 1 July 1981 and in which the user cannot influence heat consumption.
This means cases where the tenant has practically no way of controlling their own heat consumption, or where there are no adjustable radiators or any other means for the user to influence heat consumption.
**Typical examples:**
* Radiators have no adjustable thermostatic valves.
* Heat is delivered by a central system with no means of control on the user's side.
* The heat supply cannot be influenced individually in the specific unit.
**Important: H**ere you should be able to document why the tenants cannot influence heat consumption.
Homes and comparable buildings
Section 11 of the Heating Costs Ordinance also names certain types of building for which the usual rules on consumption-based heating cost billing do not fit, or fit only to a limited extent.
**These include in particular:**
* retirement homes,
* nursing homes,
* student halls of residence,
* apprentice hostels,
* and comparable buildings or parts of buildings.
What is meant are buildings whose use is reserved for particular groups of people and where, because of the special personal circumstances, ordinary rental agreements are regularly not concluded.
What matters is the special building and use structure, not just the majority group of residents. Ordinary apartment buildings in which mainly older people, students or trainees live, for example, therefore do not automatically fall under this special rule if use of the building is not expressly reserved for that group of people.
Certain heat sources and systems
An exception can also be relevant with certain types of heat supply. Under Section 11 of the Heating Costs Ordinance, rooms in buildings can be exempt where they are predominantly supplied with:
* heat from heat recovery systems,
* heat from solar installations,
* heat from combined heat and power installations,
* or heat from waste heat recovery systems.
With combined heat and power and waste heat it should also be noted that the exception is tied to the condition that the building's heat consumption is not recorded.
**Typical examples:**
* A building is predominantly supplied by solar thermal energy.
* A building predominantly uses waste heat from a technical process.
* A building is predominantly supplied by a heat recovery system.
**Important for heat pumps:**
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Heat pumps used to be named expressly in the exemption. Under the current version of the Heating Costs Ordinance this is **no longer the case**.
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Special transitional rules apply to buildings with heat pumps. Where the users' pro rata consumption of heat or hot water from heat pumps had not yet been recorded on 1 October 2024, the equipment for recording consumption generally has to be installed by the end of 30 September 2025.
Individual exemption by the competent state authority
In other individual cases the authority competent under state law can grant an exemption from requirements of the Heating Costs Ordinance.
This comes into consideration where special circumstances exist and the exemption is necessary in order to avoid unreasonable effort or other undue hardship.
**Typical cases can be:**
* exceptional structural features,
* special technical system concepts,
* disproportionate effort despite special individual circumstances,
* or hardship cases that are not sufficiently covered by the general exceptions.
**Important:** Such an exemption should be available in writing and attached to the operating cost statement as an annex.
Special case: equipment failure or other compelling reasons
A particularly important special case is equipment failure.
**Typical examples:**
* A heat cost allocator is defective and does not supply a usable value.
* A meter could not be read for technical reasons.
* A reading taken cannot be correct for compelling physical reasons.
* Measurement data has been lost because of a device fault.
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A compelling reason does not exist simply because billing by consumption is laborious or because consumption values were not organised in time. There has to be a comprehensible reason why proper recording was impossible.
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In such cases Section 9a of the Heating Costs Ordinance applies first. Under it, the missing consumption has to be determined on a substitute basis. Three methods in particular come into consideration for this:
* the consumption of the rooms concerned in comparable earlier settlement periods,
* the consumption of comparable other rooms in the same settlement period,
* or the average consumption of the building or of the group of users.
The consumption determined in this way is then used instead of the consumption actually recorded.
Only where the living or usable area affected by this substitute determination exceeds 25% of the relevant total area do the costs have to be allocated by living or usable area.
#### Recording the total consumption for heating and hot water
To record the total consumption for heating and hot water, you select whether the heating and the hot water production use **the same system** or **two separate systems**.
Recording the consumption values and meter readings does **not** differ at this point from recording them for an ordinary tenancy.
**You can find a guide for "same systems" here:**
{% content-ref url="/pages/3u9mkHROg7EEZ98kZ72s" %}
[Same system for heating and hot water](/en/anleitung/betriebskostenabrechnungen/heiz-und-warmwasserverbrauch/quadratmeter-und-zeitanteilig/gleiches-system-fur-heizung-und-warmwasser.md)
{% endcontent-ref %}
**You can find a guide for "separate systems" here:**
{% content-ref url="/pages/QH5Xfei1HcNCo4Nev5p0" %}
[Separate systems for heating and hot water](/en/anleitung/betriebskostenabrechnungen/heiz-und-warmwasserverbrauch/quadratmeter-und-zeitanteilig/getrennte-systeme-fur-heizung-und-warmwasser.md)
{% endcontent-ref %}
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