Tippapatt - istock.comThe currently approved, inexpensive heat cost allocators using the evaporation principle must be replaced by modern wireless heat cost allocators by the end of 2026.
Evaporative heat cost allocators function based on the physical principle of liquid evaporation when exposed to heat. They are considered a cost-effective but outdated technology. Since 2021, they have only been permitted in existing buildings – all devices must be replaced by modern ones by the end of 2026 at the latest. Wireless heat cost allocator be replaced.
What is the function of heat cost allocators that use the evaporation principle?
Evaporative heat cost allocators were developed as early as the 1930s. They operate on a simple but effective principle:
- An aluminum backing transfers the radiator heat to a glass ampoule.
- This contains a high-boiling liquid such as methyl benzoate or cyclohexanol
- The more heat is applied, the more liquid evaporates.
- The liquid level is read at the end of the billing period.
- Consumption is calculated as the difference to the previous year's value and is recorded in units (so-called "marks").
The method is tamper-proof, not subject to calibration requirements, and was long considered sufficiently accurate. Nevertheless, it no longer meets today's requirements.
Structure and Function in Detail
- heat conductionThe back part (usually aluminum) transfers heat from the radiator to the ampoule.
- EvaporationTemperature-related evaporation of the liquid – more heat = more evaporation
- RatingThe measured quantity is adjusted according to the radiator output. Evaluation factor offset
- Scales:
- Unit scale: Reading value × Rating factor
- Product scale: Rating factor is already integrated – direct reading possible
- No physical measurementThis is a relative measurement method, not a tariff measurement like with electricity or gas.
Why are evaporative heat cost allocators only allowed to be used until 2026?
With the new version of the Heating Cost Ordinance (HKVO, valid since 12/2021) implements the EU Energy Efficiency Directive. This means:
- For new installations, only electronic heat cost allocators with radio transmission are permitted.
- Existing buildings must also be retrofitted by the end of 2026.
- Evaporation devices fulfill the obligation to interim consumption information not
- If the building is not converted, tenants are allowed to reduce their heating costs by 3%.
Limits and restrictions on use
Evaporative heat cost allocators can be used in most modern heating systems. Since 1995, their use has also been permitted in vertical single-pipe heating systems in the former East Germany, in accordance with standards. However, there are clear limitations that must be considered during the planning phase:
- Suitable for standard radiators only
Warm air generators and damper-controlled radiators cannot be recorded because there is no suitable mounting point and the heat output depends heavily on the airflow – a factor that heat cost allocators cannot capture. - Not suitable for underfloor heating
Mounting points are missing here, and the typical surface temperatures (below 35 °C) are below the measurement limit. - Temperature limits must be observed.
The radiator temperature must reach at least 55°C on the coldest winter day (depending on the region, with an outside temperature of -10°C to -12°C). The upper limit is 110°C (only with special fluid). In practice, most systems operate between 70°C and 90°C. - Limitations of horizontal single-pipe heating systems
This installation is only possible if the pipework does not extend beyond a single unit – which is very rare in practice. The reason is the excessively large temperature difference between the first and last radiator in the circuit.
Conclusion: Evaporative heat cost allocators will soon no longer be permitted – upgrade now!
While heat cost allocators based on the evaporation principle are tried and tested, they are technically outdated. To ensure legally compliant heating cost billing, conversion to electronic radio devices is mandatory by the end of 2026. Modern systems offer more precise consumption data, automatic readings, and greater convenience for owners and residents.
Recommendations for landlords and owners
- Check your measuring equipment now – evaporators may only be used until 2026.
- Plan the switchover well in advance to avoid bottlenecks during the conversion process.
- Inform your tenants about the advantages of modern wireless technology.
Jacob Ammentorp Lund – stock.adobe.comUpgrade to radio now!
With the LoRaWAN radio system Brunata Minol Connect, you create the basis for digital heating cost billing.
This is how landlords and property managers can collect consumption data securely, digitally and transparently.
InsideCreativeHouse – AdobestockAlways up to date
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