Dividing costs with a heat meter

Heat meters are helpfully replacing calorimeters, which are more common in housing but less reliable. Moreover, the installation of individual heat meters (per dwelling or apartment) allows one to precisely measure the actual consumption of each unit. However, it must not be forgotten that various fixed costs will have to be divided among the different users.

Examples of costs to divide:
> Cost of deliveries and consumption of fuels
> Cost for the production of domestic hot water if this is centralized
> Power supply used for the entire heating system
> Service, monitoring and maintenance of the equipment
> Possible future measures required by legislation, for example anti-pollution control
> Chimney sweeping
> Regular examination of the equipment and its security
> Cleaning and setting up of operation premises
> The cost for the equipment to measure energy consumption, including the drawing up of invoices and calculating how to divide costs (in other words, between the calorimeters, heat meters and the cost of services from the service provider).
In this case, we can distinguish between variable costs (consumption of fuel) and fixed costs (shared costs of heating the building: heating of halls, corridors, stairways, etc.).

How to determine the percentage of fixed costs?

Different factors can be taken into account to determine the percentage of fixed costs to apply for a building. We thus take into account the entirety of the building: an apartment that is very warmly heated will contribute to the building’s thermal envelope, or at least to the neighboring apartments, which will thus not need to heat themselves as much. The inverse is true for an insufficiently heated apartment. That’s why one initially deducts from the totality of the heating costs a part which will be portioned out in fractions.

The following elements may be taken into account to determine this percentage:
> the configuration of the building (if the units don’t have many shared walls, indirect heating will be reduced)
> the insulation of units (external insulation and insulation between units limits indirect heating)
> the behavior of residents (to encourage residents who do not save much energy, one can opt for a percentage of variable costs that is as high as possible)

In practice, the rate of fixed costs is, in general, between 20 and 50%. It should be noted that the manner in which costs will be divided must be set at the beginning of the billing period and that any change must be communicated in due form to the residents. INDEX+ can help you determine this rate based on the building’s characteristics.

Calculating the division of costs

To be able to divide heating and, potentially, water costs among the different units, the following elements must be taken into account:
> Readings of meters and/or calorimeters at the beginning and end of the period
> Costs of the purchase of fuel (gas, fuel oil, pellets, etc.) during the period and taking into account, in the case of fuel oil and pellets, the difference in stocks between the end and the beginning of the period.
> Boiler maintenance fees
> Chimney sweeping fees
> Electricity costs for the heating system (if there is no meter installed, this consumption can be estimated)
> Energy metering fees, including the cost of installing and maintaining equipment to divide costs (water meters and heat meters or calorimeters) as well as the cost of services by a specialist company.

When domestic hot water is measured using water meters, the energy required for its heating can be estimated by using the values in norm DIN 4713, part 5.
For the division of the fixed costs of heating, the most common way in which costs are divided is a ratio based on the surface area of the different units.