> 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/wasserverbrauch/quadratmeter-und-zeitanteilig.md). # Square metres and pro rata time In this step you choose how the building's water consumption is to be allocated across the individual units. Alongside allocation using **meters and meter readings**, you can also allocate water consumption by **square metres and pro rata time**. Use this option where **no water meter exists for at least one unit** or at least one meter reading was not taken. The total water consumption is then allocated according to the floor area share of the respective units. Immodio automatically recognises whether a move-in, move-out or vacancy was documented for a tenancy during the billing year and additionally calculates the respective share **pro rata by time**. {% hint style="info" %} Where usable water meters exist for all units, billing should generally be based on consumption. {% endhint %}
### What does "square metres and pro rata time" mean? With this method the building's total water consumption is not allocated according to individual meter readings but according to the floor area share of the respective unit. The calculation is based on the following principle: > Share of the unit = living or usable area of the unit ÷ total living or usable area of the building If a unit was not used or let for the entire settlement period, the calculation is also made pro rata by time. The unit is then only taken into account for the period during which it was assigned to the respective user. Example: > An apartment has 80 m².\ > The building has 400 m² in total.\ > The apartment was let for 6 of 12 months.\ > The floor area share is 20%, which is then reduced pro rata to 6 months. ### When may allocation by square metres be used? Allocation by square metres is permissible under the Operating Costs Ordinance (BetrKV) where water consumption is not recorded in full for all units. The Federal Court of Justice has ruled that landlords are not obliged to allocate by consumption as long as not all rented apartments in a building are fitted with water meters. In that case water and drainage can be allocated by living space. {% hint style="info" %} The same applies where **almost** all units have a water meter but **at least one unit does not**. As long as consumption is not recorded in full for all tenants, billing does not necessarily have to be based on individual consumption. {% endhint %} ### When should this option be used? Use **"Square metres and pro rata time"** if: * there are no individual water meters for all units, * individual units cannot be measured reliably, * meter readings are missing or unusable, * the rental agreement or the previous statement provides for allocation by floor area, * water consumption is to be allocated as general building consumption. {% hint style="warning" %} This method is relevant for **cold water** and any associated **drainage costs**. It does **not** replace the special rules for heating or hot water costs. {% endhint %} ### When may this option not be used? This option should not be used as a pure floor area allocation where the water consumption of all units is recorded fully and reliably. In that case the billing measure has to take appropriate account of the differing consumption. Where consumption is recorded, Section 556a BGB requires a consumption-based or at least consumption-appropriate measure. ### Vacancies Vacant units may not simply be excluded from the total floor area. The share attributable to vacant units is generally to be borne by the owner or landlord. The Federal Court of Justice emphasises that the vacancy risk may not be shifted unreasonably onto the other tenants. In practice this means that vacant apartments remain part of the total floor area. Their share is not allocated to the other users but assigned to the owner or landlord. Immodio handles this assignment for you automatically. ### What has to be considered for commercial or special uses? **What has to be considered for commercial or special uses?**\ In mixed-use buildings, for example with apartments and commercial units, a prior deduction may be necessary. This applies in particular where a commercial unit causes considerably higher water consumption and residential tenants would be burdened significantly more by allocation according to floor area. The Federal Court of Justice has ruled (see **BGH, VIII ZR 188/07**) that a prior deduction of the costs attributable to commercial space is permissible or required where the commercial use leads to a significant additional burden on residential tenants. This can be relevant for water-intensive uses such as * restaurants, * hairdressers, * launderettes * or comparable businesses. {% hint style="info" %} A prior deduction is not, however, automatically required for every business. What matters is the specific type of operating cost, the actual use and whether it causes significant additional costs. {% endhint %} ### Drainage The Operating Costs Ordinance distinguishes between **water supply** and **drainage**. Water supply is Section 2 no. 2 BetrKV, drainage is Section 2 no. 3 BetrKV. Even though waste water charges are often based on fresh water consumption, rainwater or surface water charges do not necessarily depend on individual water consumption and should be treated separately. {% hint style="info" %} In Immodio you can use the category **"Costs for rainwater"** for this. {% endhint %}