Calculation ofIDC : the heat expenditure index

What is the IDC ?

The heat consumption index (IDC) is an indicator of the energy consumption of a building to cover its heat needs (heating and domestic hot water).
Expressed in megajoules per square metre per year (MJ/m2a), it represents the annual amount of final energy consumed for heating and domestic heat water production, based on one square metre of heated surface and corrected for the climatic data of the year in question.


Why calculateIDC ?

The calculation of IDC allows:

- Evaluate and compare the energy performance of a building from one year to the next;
- Detect possible malfunctions;
- Check the effectiveness of the improvement measures implemented and compare it with a building of the same category.

Who are the owners concerned?

The following owners are subject to theIDC regime, i.e. they are obliged to calculate and transmit annually theIDC of their building to the ESO:

- Owners of residential buildings with 5 or more heat consumers (i.e. those with at least 5 dwellings).

- Owners of heated buildings of other categories, i.e. those occupied by a trade, office or industry (or several), e.g. a shop, workshop, engineer's office, solicitor's office, doctor's surgery, coachbuilder, hotel, church...

- Owners of mixed buildings, i.e. those that include one or more dwellings and one or more commercial or industrial activities.

The owners of villas, are now also concerned, from January 2023 by the obligation to calculate and transmit theIDC, except when applying for Subsidies for the CECB Plus

Thresholds set out in the Energy Act Regulations

On September 1, 2022, the threshold for the heat expenditure index (IDC) was lowered to 125 kWh/ (450 MJ/
If your IDC is between 125 and 153 kWh/m2.year (450 and 550 MJ/m2.year), you'll simply need to implement optimization measures. But if your IDC is really too high (currently set at 222 kWh/m2.yr, or 800 MJ/m2.yr), you'll need to carry out real energy renovation work. Don't worry, this "significant" threshold will be progressively lowered over the years to clean up the entire building stock. So, let's say we all have 10 years to bring our buildings into line with the 2032 deadline: (Fiuuuuu! Still, Hein... 😌)
The energy work to be undertaken includes insulating the building envelope, changing the energy used, installing solar collectors and recovering the heat released. Optimization measures include:

  • an optimization contract
  • improvement of ventilation
  • pipe insulation and heating pump replacement as well as thermostat installation and much more.

If you need to provide a calculation of your IDC, you have until June 30th of the following year to do so. If you need help, you can call on a dealer approved by the cantonal energy office like us. Finally, if you are an owner of a building for professional use, you should know that you will have to publish your IDC on your website from 2023. So don't forget to check your IDC before it becomes an energy hog!

Our services 

  • Call on our certified expert to calculate your IDC.
  • TheIDC is offered with our CECB+ service.

For more information on the change in the Regulations, see our article

Contact us

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