A heat-cost allocator does not measure kWh. It records, over time, the gap between the radiator's surface temperature and the room temperature, then turns that history into dimensionless allocation units weighted by a coefficient specific to the emitter. The only physical quantity in the file remains the consumption read at the boiler room: the allocator merely shares out its variable portion between the homes.
The obligation does not cover the whole stock either. The French arrêté of 6 September 2019 excludes buildings whose heating consumption stays below 80 kWh/m² of habitable floor area per year, and article R. 241-7 of the energy code opens two further exemptions, technical impossibility and a cost that is excessive against the expected savings, both of which must be justified in writing and filed with the building's maintenance log.
HCA in collective heating: what the allocator actually measures
How an HCA works: sensors, indices and consumption calculation
An HCA is fixed to each radiator. It tracks the emitter's temperature over time, and depending on the model, sometimes the room temperature too. The device converts this history into index units. It is not a kWh measurement. The calculation factors in a coefficient tied to the radiator (output, shape) and sometimes its installation, to compare different emitters within the building.
Difference between an HCA and individual energy metering: what changes on the bill
With an energy meter, you bill kWh measured on your loop (flow rate and temperature difference). With an HCA, you allocate a collective boiler-room consumption. The bill retains a shared portion (losses, common areas), then a variable portion based on each home's indices.
Four families of device coexist in the residential stock, and they are neither read nor challenged in the same way.
| Device | Quantity read | Unit returned | Where you meet it |
|---|---|---|---|
| Heat meter | flow rate and temperature difference on the home's loop | kWh | horizontal distribution, one loop per home |
| Electronic allocator, two sensors | radiator temperature and room temperature | allocation units | risers, mixed emitters |
| Electronic allocator, one sensor | radiator surface temperature only | allocation units | high, stable flow temperature across the season |
| Evaporation allocator | volume of ampoule evaporated over the heating season | allocation units | older stock, annual on-site reading |
Only the first line produces an energy figure. The other three produce a sharing key, and that is exactly what should be said to the managing agent before installation rather than after the first service-charge reconciliation.
Typical cases in collective buildings: risers, old networks and mixed emitters
On risers and old networks, circulation imbalances and blocked valves quickly affect the indices. When emitters are mixed (cast iron, convectors, towel radiators), the coefficients become sensitive. Hydraulic balancing and coherent controls avoid "heating the stairwell" more than the rooms.
Technical limits of the HCA in the field: reliability and allocation discrepancies
Errors linked to placement and radiator type: cast iron, steel, convector
An HCA reads a surface temperature. Depending on the installation (in the middle, too low, near a curtain or a recess), the measurement drifts. Even with a suitable coefficient, a high-inertia cast-iron radiator and a steel panel do not heat up the same way. On a convector, the front panel can stay "cold" while the room heats up. Result: possible measured discrepancy between homes.
Influence of free heat gains: sunlight, cooking, appliances and corner units
Free heat gains blur the allocation. A south-facing living room, a frequently used kitchen, appliances that give off heat, or a corner unit with more cold walls, all change the actual need. The HCA does not always see this dynamic and can over- or under-count, especially during shoulder seasons. Keep free heat gains in mind during analysis.
Settings, coefficients and maintenance: when the allocator no longer matches reality
Reliability depends on the settings and follow-up. Coefficients not updated after a radiator change, blocked thermostatic valves, missing hydraulic balancing, or a degraded sensor. Without checks, the indices become an imperfect snapshot. Plan for regular verification and recalibration after work. Otherwise, factory settings no longer match the field.
Regulatory limits and obligations in 2026: what you must check in collective buildings
When installing an HCA is mandatory, exempted, or contestable in co-ownership
In collective heating, HCAs are in principle required when individual allocation is possible and proportionate. An exemption exists if installation is technically impossible or if the gain is deemed insufficient relative to the cost. In co-ownership, a challenge is decided on these criteria, with written supporting evidence.
Cases of technical impossibility are not argued, they are read off the annex to the arrêté of 6 September 2019. Here are the ones you meet on site and the document that holds them up under inspection.
| Situation found in the building | Applicable regime | Document to file |
|---|---|---|
| Heating consumption below 80 kWh/m² of habitable floor area per year | outside the scope of the obligation | boiler-room consumption divided by habitable floor area |
| A single loop serving several homes | technical impossibility | network drawing and riser identification |
| Emitters wired in series on a one-pipe circuit | technical impossibility | hydraulic schematic and emitter count per loop |
| Underfloor heating with no per-home measurement | technical impossibility | evidence that no per-home manifold exists |
| Warm-air heating | technical impossibility | description of the generator and air distribution |
| Cost excessive against the savings | economic exemption | ten-year discounted whole-life cost, 15% savings assumption |
The last case is the one worth working on. The arrêté sets the method: a whole-life cost discounted over ten years, compared with a conventional 15% saving on heating consumption. A low-consumption block with many small flats quickly falls on the right side of the calculation, provided the note is produced, dated and kept with the maintenance log.
Informing occupants and transparency: documents, readings and explanations to provide
Before and after installation, plan for clear information. User instructions, calculation method, reading schedule, and access to the indices must be shared. With remote reading, also explain data protection and who can view what. Goal: charges that are understandable.
Link with balancing and controls: prerequisites before installing allocators
Without a balanced network, HCAs mainly measure installation defects. Check hydraulic balancing, controls (outdoor sensor, heating curve, thermostatic valves where relevant) and the condition of the emitters. Otherwise, you risk discomfort discrepancies and disputes.
HCA and energy retrofits: limits for guiding effective work
Why an HCA does not replace an energy audit: reading consumption vs. causes
A good indicator, the HCA (often based on heat-cost allocation) shows consumption. But it does not say why a home overheats. The energy audit, on the other hand, links the figures to causes. Thermal bridges, ventilation, settings, usage, everything is reviewed to decide on the right work. Those causes are pinned down faster when the property is reconstructed from public databases and consumption data before the visit even starts.
Effects after renovation work (insulation, joinery, heat pump): tricky before/after comparisons
After insulation, new joinery or a heat pump, comparing "before" and "after" remains fragile. Weather, occupancy rate, setpoints, hot water, everything shifts. Without weather correction and monitoring over several seasons, the weather effect can mask or amplify the actual gain.
Situations where the collective building gains more from controls: thermostatic valves, sensors, heating curve
In collective heating, quick gains often come from controls. Thermostatic valves, well-placed sensors, a heating curve set and monitored, avoid "running flat out" to compensate. Before launching major work packages, a clean adjustment and regular measurement bring performance back on track. To go further on verifying gains, post-renovation consumption monitoring is often essential.
Practical advice for tradespeople: installing better, explaining better, preventing disputes better
Preparing the job: identifying emitters, photos, radiator data sheets and validations
Before installing heat-cost allocators, do a room-by-room survey. Take dated photos of every radiator, note the type, dimensions, location, and create a radiator data sheet with the associated device number. Have the list validated by the property manager and, if possible, by the occupant. Fewer blind spots, fewer disputes. That survey stays usable when the technician documents every emitter, photos and dimensions included, from their phone.
A simple explanation for the property manager and occupants: HCA limits and good usage practices
Clearly explain that an HCA is not an energy meter. It helps allocate a collective bill based on indices, so usage matters. Advise against covering radiators, keeping access to the devices clear, and avoiding extreme variations (a window left open continuously, a covered radiator). A simple message defuses tension.
Control plan: readings, replacement, seals and complaint handling
Set up a routine. Initial reading, checking the fixings, a seal number recorded, then traceability in case of replacement. For a complaint, ask for photos, check the radiator's identification, and document each action. A clean file protects the company as much as the client.
