I for IMSER

In an economy with an increasingly dematerialised, digital focus, understanding where the heart of consumption lies is not just a statistical challenge, but a strategic necessity. This was the goal which the IMSER - the Monthly Services Electricity Consumption Index was created to achieve. The indicator was designed and developed by Terna to provide institutions and analysts with a roadmap to guide them through the consumption classes of what was once known as the Tertiary sector: hotels, restaurants and bars; public administration and defence; professional, scientific and technical activities; trade; finance and insurance; real estate; information and communication; education; health and social care; veterinary services; transportation and storage; and other services.

The origins of the IMSER. The IMSER, following in the footsteps of the IMCEI - Monthly Industrial Electricity Consumption Index, was consolidated in 2020 with historical data from 2019. The need for such fine-tuned monitoring became apparent during the Covid-19 pandemic, when the mobility of people and companies was tethered to ATECO codes. This led to the Italian Regulatory Authority for Energy, Networks and the Environment (ARERA) asking Terna to monitor in real time how the various sectors were reacting to the restrictions.

While the IMCEI analyses the large, energy-intensive companies directly connected to the high-voltage transmission grid and the so-called interruptible medium-voltage customers, the IMSER has been created to map the “broader tertiary” sector, which is often connected to distribution. With the industrial index accounting for around 30% of the sector (about 10% of national consumption), the IMSER represents a much broader segment, covering 80-85% of the entire services area (about one quarter of national consumption).

Prior to the development of the IMSER, economic trends in Italy were assessed almost exclusively through industrial consumption. Today, however, the situation has changed: the expansion of the tertiary sector has led to services generating over 70% of GDP, introducing greater volatility. In fact, the dynamics of how sectors like tourism and logistics react to external shocks are very different from those of heavy industry. Despite the significance of these changes, a considerable information gap persisted in the absence of a timely tool capable of isolating the tertiary sector to provide a clear, “near-real-time” snapshot. This is precisely the knowledge gap that the IMSER was created to fill.

How the IMSER works. The index does not consist of a mere summation of consumption, but adopts a rigorous methodology based on real data for withdrawal from the electricity grid. Its structure is broken down into two essential macro-categories: the data are aggregated by Product Category and by Province. What’s more, thanks to the digital platforms made available by Terna, it’s possible to make comparisons with previous months and years.

Terna relies on contributions from the main distribution grid operators for the index data. Each month, they provide consumption values broken down by ATECO code and area:

• e-distribuzione (Enel), which guarantees coverage of 106 provinces out of a total of 110;
• Edyna for the province of Bolzano;
• UNARETI and DUERETI for the Milan and Brescia areas;
• Areti (Acea) for the Rome area;
• Deval for Valle d’Aosta.

Given the time needed to take and process readings, the IMSER index comes with an unavoidable delay of about two months compared to the IMCEI. However, the IMSER is of far more than statistical importance, as it acts as an invaluable tool for economic analysis. In fact, thanks to its timely nature, this monthly publication often scoops the official ISTAT data, offering details by sector that reveal trends in the segments, indicating potential signs of recovery or slumps. For instance, an increase in consumption related to “Communications” may herald a development in the sector of IT and Data Centres. At the same time, the index supports energy planning by predicting where more energy will be required and, potentially, how to optimise the national grid based on the new tertiary hubs.

2025 closes with the IMSER up: +2.9% compared to 2024. According to Terna’s data, electricity consumption by Services underwent an overall growth of 2.9% in 2025, compared to the values for the previous year. Many classes showed an upward trend; for instance, the category of information and communication closed the year on a double-digit increase (+11.9%). Positive values were also recorded for public administration and defence (+5.4%) and real estate (+1.8%).

The Data Portal, the dashboard with all the information. Terna makes all this information available through the Data portal which serves as an analysis tool for various players on the Italian stage. By using the index to refine macroeconomic calculations, institutions like the Bank of Italy and the Italian Ministries of Economy and Finance and of the Environment and Energy Security can thereby achieve a clearer picture of the dynamics at work. At the same time, trade associations in crucial sectors constantly monitor the IMSER to support their predictions, comparing them with real consumption. Finally, the data offer vital indications for planning and investments: observing the growth of consumption in specific sub-classes yields clear signs of where future investments in infrastructure would be most fruitfully directed. In short, the IMSER data serve to monitor the vitality of our cities and the progress made in the process of modernising the entire nation.

IMSER and IMCEI: the differences. Although both indexes are prepared by Terna to take the pulse of the Italian economy through electricity consumption, the IMSER and the IMCEI differ profoundly in both their scope and the characteristics of the subjects of their monitoring.

The main difference lies in the object of their analysis: the IMCEI mainly monitors consumption by businesses that consume vast quantities of energy, belonging to key sectors of Italian industry. The IMSER, on the other hand, covers the wide world of services.

This distinction is also reflected in how the energy is withdrawn. The IMCEI targets large industrial customers connected directly to the high-voltage and extra-high-voltage national transmission grid, as well as the interruptible medium-voltage customers whose withdrawals Terna monitors on a monthly basis. The IMSER, instead, monitors businesses which are often connected to the medium-voltage and low-voltage grid, with immensely varied consumption profiles. This fragmentation makes the preparation of the IMSER more technically complex, as it requires the aggregation of data sourced from a far broader and less centralised pool than the major industrial hubs. This also means a more spread-out distribution across the territory.

In terms of the analysis, the two indexes offer complementary yet distinct readings. The IMCEI acts as an early indicator of industrial production, shedding light on the acceleration or slow-down of activities in factories and the efficiency of production processes. The IMSER, instead, serves as a thermometer gauging the quantity of energy used over months and years by the services sector.

The history of the two tools also shapes their identity. The IMCEI can boast a well-established history and extreme precision, thanks to Terna’s official responsibility for measurements on the transmission grid since 2017, guaranteeing validated data in just a few days. The more recent IMSER was created specifically to complete the picture with the information missing from the industrial perspective. Together, they allow Terna to provide an overall vision of the Italian system.