Energy metering for DHW, heating and cooling services

1. Energy metering systems

Energy metering for domestic hot water production (DHW), heating and cooling services is a key component in promoting energy efficiency and reducing unnecessary consumption in buildings with centralised systems, both new and existing. Specifically, these systems allow the autonomous and independent management of the above-mentioned final uses in buildings with a centralised system or connected to a district heating network. Therefore, they are fundamental elements for reducing energy consumption, and related costs and greenhouse gas emissions, as well as for actively engaging and empowering end-users. Meters come in two varieties:

• Direct meter, that measures the actual energy consumption of each individual building unit through devices installed directly at the energy consumption points of each user. This system provides accurate and detailed measurement of the consumption of each individual building unit, as well as enabling continuous monitoring and, consequently, optimised energy management. Indeed, energy costs are allocated fairly based on real consumption, incentivising users to reduce wasting.
• Indirect meter, that estimates the energy consumption of individual building units based on indirect criteria. In detail, such a system does not use metering devices for each individual building unit, but the total building energy consumption is measured by a central device and, subsequently, distributed on the basis of the energy demand thousandths calculated according to UNI/TS 11300-2:2019 [1]. Therefore, indirect meters find their application in buildings where it is not possible to install direct individual meters.

Two categories of energy metering systems can be distinguished, modules and satellites, which are essential components in energy management and metering. These systems are designed to collect, transmit and analyse energy consumption data, ensuring accurate control and efficient management of the resources. In detail:

• Metering modules distribute the heat transfer fluid and the domestic hot (DHW) and cold (DCW) water from the central heating and cooling plant to the individual residential units. At the same time, they are equipped with the necessary devices for measuring and recording the thermal energy consumption and the DHW and DCW volumes. They can also manage the measurement function associated with the DHW recirculation circuit.
• Metering satellites perform the same functions as modules, but are generally - though not exclusively - not designed for cooling management. The main feature that distinguishes them from modules is that they are equipped with a primary heat exchanger, so that the primary distribution network is decoupled from the secondary circuit of the residential unit. DHW is produced by means of an instantaneous heat exchanger installed on board the satellite.

Finally, a fundamental aspect in guaranteeing the correct distribution of flow rates to the building units is the integration of the metering devices with the balancing systems. It is appropriate to install balancing valves and differential pressure regulators, whose purpose is to regulate the water flow rates in the different sections of the hydronic network, ensuring an even distribution of thermal energy and avoiding energy wastage and anomalies in system operation.

2. National and international reference legislation for energy metering systems

In Italy, the application of energy metering systems is regulated by various regulations and decrees, with the aim of improving energy efficiency and reducing consumption in buildings. The main reference regulations are:

• Legislative Decree 102/2014 [2]: Legislative Decree No. 102 of 4 July 2014 transposes Directive 2012/27/EU [3] on energy efficiency. The regulation requires the installation of heat metering devices in buildings with centralised heating, cooling and domestic hot water systems, and the allocation of energy costs according to the actual consumption of each building unit.
• Legislative Decree 141/2016 [4]: Legislative Decree No. 141 of 18 July 2016 amends the previous Legislative Decree 102/2014 and introduces further clarifications with regard to the obligations for costs accounting and allocation. In particular, for all buildings with several dwellings equipped with a centralised system for heating, cooling and domestic hot water production, it establishes the obligation to account for heat individually.
• Legislative Decree 73/2020 [5]: Legislative Decree No. 73 of 14 July 2020 implements Directive 2018/2002/EU [6], which amends the previous Directive 2012/27/EU on energy efficiency. In particular, this decree strengthens the obligations for individual heat and energy metering in buildings, introducing measures to improve transparency and efficiency in the use of energy and establishing clear criteria for assessing the technical and financial feasibility of installing such systems.
• UNI 11388:2015 [7]: came into force on 28 May 2015, replacing the previous UNI/TR 11388: 2010 [8]. This standard defines the criteria and guidelines for the design, installation, testing and maintenance of heat metering devices in both residential and non-residential buildings with centralised heating systems.  
• UNI 10200:2018 [9]: came into force on 11 October 2018, replacing the previous UNI 10200:2015 [10]. This standard defines the criteria for allocating the costs of heating, cooling and domestic hot water production in buildings with centralised systems. It introduces the concept of "fixed" and "variable" heating costs. In addition, it provides the methods for calculating the costs allocation based on the metered consumption for each building unit.

At the international level, several standards and directives regulate the implementation of energy metering systems and provide guidelines for the design, installation, operation and maintenance of such systems. Below are the main European directives and ASHRAE standards that provide a comprehensive framework for energy metering systems:

• Directive 2012/27/UE [3], known as the Energy Efficiency Directive, it establishes a framework of measures to promote energy efficiency in the European Union. Among other provisions, this Directive includes specific requirements for energy metering in buildings with centralised heating, cooling and domestic hot water systems. In particular, it establishes the obligation to install individual metering systems for heating and DHW in multi-apartment buildings with centralised systems (Article 9: 'Metering'). Furthermore, in Article 9.3 ("Technical and economic feasibility"), the Directive requires the implementation of individual meter only if it is technically feasible and cost-efficient; otherwise, alternative cost allocation methods based on consumption estimation must be considered.
• Directive 2018/2002/UE [6] is a further step towards improved energy efficiency and greater transparency in energy metering, updating and strengthening the measures set out in the previous Directive 2012/27/EU.
• ASHRAE Guideline 14 (“Measurement of Energy, Demand and Water Savings”) [11] provides guidelines for measuring and verifying energy savings in buildings and facilities. Although not focused on energy metering, the guide is relevant in establishing principles and practices for accurate energy savings assessment. Therefore, the document is an essential guide to ensure that energy metering and savings assessment are carried out in an accurate and methodical manner.
• ASHRAE Standard 135 (“Building Automation and Control Network - BACnet”) [12] specifies a communication protocol for building automation and control systems, including energy monitoring and metering systems.

3. Implications in design strategies for implementing energy metering

Key strategies for designing and realizing effective metering systems include: (i) integrated design, right from the building design phase, using advanced technologies to improve the collection and analysis of energy data, and planning the installation of metering and monitoring systems; (ii) the use of centralised systems to facilitate the management and monitoring of energy consumption, through integration with individual meters for each building unit; (iii) automation and control for real-time monitoring and management of energy consumption through integration with building automation and control systems (BACS); (iv) the use of distributed control systems to monitor and manage consumption in different zones of the building allowing precise and tailored control of heating, cooling and hot water production. These design strategies can ensure an efficient energy metering system, helping to reduce energy consumption, optimise resources and achieve sustainability goals.

4. Reference

• UNI/TS 11300-2:2019. Prestazioni energetiche degli edifici - Parte 2: Determinazione del fabbisogno di energia primaria e dei rendimenti per la climatizzazione invernale, per la produzione di acqua calda sanitaria, per la ventilazione e per l'illuminazione in edifici non residenziali, 7 febbraio 2019.
• Decreto Legislativo 4 luglio 2014, n. 102. Attuazione della direttiva 2012/27/UE sull'efficienza energetica, che modifica le direttive 2009/125/CE e 2010/30/UE e abroga le direttive 2004/8/CE e 2006/32/CE. (14G00113) (GU Serie Generale n.165 del 18-07-2014).
• Direttiva 2012/27/UE del Parlamento Europeo e del Consiglio del 25 ottobre 2012 sull'efficienza energetica, che modifica le direttive 2009/125/CE e 2010/30/UE e abroga le direttive 2004/8/CE e 2006/32/CE. (GU L 315/1 del 14-11-2012).
• Decreto Legislativo 18 luglio 2016, n. 141 . Disposizioni integrative al decreto legislativo 4 luglio 2014, n. 102, di attuazione della direttiva 2012/27/UE sull'efficienza energetica, che modifica le direttive 2009/125/CE e 2010/30/UE e abroga le direttive 2004/8/CE e 2006/32/CE. (16G00153) (GU Serie Generale n.172 del 25-07-2016).
• Decreto Legislativo 14 luglio 2020, n. 73. Attuazione della direttiva (UE) 2018/2002 che modifica la direttiva 2012/27/UE sull'efficienza energetica. (20G00093) (GU Serie Generale n.175 del 14-07-2020).
• Direttiva 2018/2002/UE del Parlamento Europeo e del Consiglio dell'11 dicembre 2018 che modifica la direttiva 2012/27/UE sull'efficienza energetica. (GU L 328 del 21-12-2018).
• UNI 11388:2015. Sistemi di contabilizzazione indiretta del calore basati sui tempi di inserzione dei corpi scaldanti compensati dalla temperatura media del fluido termovettore. 28 maggio 2015.
•  UNI/TR 11388:2010. Sistemi di ripartizione delle spese di climatizzazione invernale utilizzante valvole di corpo scaldante e totalizzatore dei tempi di inserzione. 11 novembre 2010.
• UNI 10200:2018. Impianti termici centralizzati di climatizzazione invernale, estiva e produzione di acqua calda sanitaria - Criteri di ripartizione delle spese di climatizzazione invernale, estiva e produzione di acqua calda sanitaria. 11 ottobre 2018.
• UNI 10200:2015. Impianti termici centralizzati di climatizzazione invernale e produzione di acqua calda sanitaria - Criteri di ripartizione delle spese di climatizzazione invernale ed acqua calda sanitaria. 11 giugno 2015.
• ASHRAE. ASHRAE Guideline 14: Measurement of Energy, Demand and Water Savings. American Society of Heating, Refrigerating and Air-Conditioning Engineers, 2023.
• ASHRAE. ASHRAE Standard 135: Building Automation and Control Network (BACnet). American Society of Heating, Refrigerating and Air-Conditioning Engineers, 2016.