Methodology: how the IDC benchmark is calculated

What the IDC measures

The indice de dépense de chaleur (IDC) is the official Geneva indicator of a building's heat consumption: final energy used for space heating and domestic hot water, divided by the heated floor area (SRE), corrected for the severity of each winter (degree-days). It is expressed in MJ/m² per year (3.6 MJ = 1 kWh) and declared every year by building owners, one value per building (EGID).

The IDC does not include process energy, cooling, lighting or equipment. For district heating, the delivered heat is counted; for heat pumps, the electricity used is counted — which makes heat-pump buildings look lower than fuel-based ones.

Which buildings are shown

Buildings whose footprint lies mainly (≥ 50 % of the area) inside an industrial zone managed by the FTI foundation. When no zone covers half of the footprint, a point inside the building decides; otherwise the building is unassigned. The assignment method is stored for each building.

Peer benchmark

  • Peer group: all buildings of the same type (e.g. industrial, logistics, offices) across the canton of Geneva, in the same year. Types group the official SITG building uses.
  • Peer median: the middle IDC value of the group.
  • Difference: (IDC − peer median) / peer median.
  • Percentile: share of the group with a lower IDC. The 84th percentile means a higher IDC than 84 % of similar buildings.
  • If a group has fewer than 10 buildings, no benchmark is shown.
  • Zone median is shown as context only when the zone has at least 10 buildings in that year.

Trend and estimated energy

  • 3-year trend: change between the latest IDC and the IDC of the same building three years earlier. Because the IDC is climate-corrected, years are comparable.
  • Estimated final energy = IDC × SRE / 3600, in MWh per year, climate-normalised. It is an order of magnitude for heating and hot water, not a metered total.

Legal thresholds (indicative)

Geneva's energy regulation uses the average IDC of the last three years. Above 450 MJ/m², owners must take improvement measures. Above the "significant" threshold, an energy renovation is mandatory: 800 MJ/m² until the end of 2026, 650 from 2027 and 550 from 2031. ThermoGeneva compares the published 3-year average with these values for information only; obligations are determined by the cantonal energy office (OCEN).

Data quality rules

  • Records without EGID, with an implausible year or a negative IDC are rejected.
  • Duplicates (same EGID and year) are resolved deterministically: most recent entry date, then highest source identifier.
  • An invalid heated area is set to empty, so no energy estimate is computed for that record.
  • If the official source changes its structure, the update stops instead of publishing inconsistent data.

Limitations

Values are self-declared by owners and depend on the declared heated area. Peer groups mix buildings of different ages and sizes. A high value is a reason to look closer, not a verdict: ThermoGeneva is a screening tool, not an energy audit.

Official sources