Energy production: fossil and renewable energy sources

[GRI - 203-2],


Through Acea Produzione, Acea Ambiente, Orvieto Ambiente, Deco and Ecologica Sangro, the Group produces electricity pri- marily from renewable sources. The majority of production is provided by hydroelectric plants and another significant portion, also partially renewable, from waste-to-energy plants utilising paper-mill waste and Solid Recovered Fuel (SRF).
Acea continued to grow the photovoltaic sector, in accordance with the current Business Plan. As of March 2022, this aim has been sup- ported by a financial transaction under which Acea transfers its exist- ing photovoltaic assets — which are either already in operation or in the process of being connected to the grid — to a Company of which Acea Produzione is a minority shareholder180, while retaining control of the management of the plants, and has signed agreements aimed to purchase the renewable energy produced by the plants.
Lastly, Acea Produzione also has fossil fuel (thermoelectric) pro- duction plants, mainly relating to the high-eciency cogeneration plant at the Tor di Valle power station, which had the highest avail- ability during the year.
The power park includes:

  • 7 hydroelectric power stations located in the Lazio and Abruzzo regions for a total of 119.3 MW;
  • 2 thermoelectric power stations located within the Municipality of Rome area: Montemartini (78.3 MW)181 and Tor Di Valle (28.5 MW), for 106.8 MWe total available installed capacity;
  • a photovoltaic park for a total of 16.7 MW182 (total capacity, including the plants owned by the investee company and not consolidated on a line-by-line basis, is 101 MW).

The generation of energy from waste-to-energy processing is managed by Acea Ambiente, taking place at two plants located in San Vittore del Lazio and Terni, and both with percentages of biodegradable material

(renewable source) varying between 40% and 50%. The total gross electrical power currently available is approximately 62.5 MWe183.
In addition, the Environment Business produces renewable electricity using biogas derived from the anaerobic digestion process at the Orvieto Ambiente Technology Hub, the sites managed by Deco and the Acea Ambiente composting plants of Aprilia and Monterotondo Marittimo.

The Company Ecogena, certified as an ESCo (Energy Services Company) in accordance with UNI CEI 11352:2014, develops the energy eciency initiatives for the Group and reports their results to Gestore dei Servizi Energetici (GSE) for the awarding of Energy Eciency Certificates (EEC).

The activities assigned to Ecogena include also the design and building of cogeneration and trigeneration plants184 for the production, in combined mode, of electrical, heat and cooling energy.
The total production capacity of the cogeneration plants managed by Ecogena, combined (or not) with district heating networks, amounts to a total electrical output of 3.9 MW, located in areas across the Lazio region.

Table no. 54 – Installed power of the electric power stations of Acea Produzione

hydroelectric power stations thermoelectric power stations
A. Volta di Castel Madama (Rome) power station gross power 7.4 MW Tor di Valle power station – high-efficiency cogeneration section (CAR) (*) (Rome) Methane fuel - gross power 28.5 MW
G. Ferraris di Mandela (Rome) power station gross power 5.9 MW Montemartini power station (Rome) Diesel fuel - gross power 78.3 MW
Salisano power plant (Rieti) gross power 25.0 MW  
G. Marconi di Orte power plant (Viterbo) gross power 21.8 MW  
Sant’Angelo power plant (Chieti)
gross power 58.4 MW
Cecchina power plant (Rome) gross power 0.4 MW  
Madonna del Rosario power plant (Rome) gross power 0.4 MW  
general total: gross capacity 226 MW

(*) The CAR plant in Tor di Valle provides district-heating service in the area south of Rome.

Installed capacity, which totals185around 320 MW (404 MW including the Investee company not consolidated on a line-by-line basis), is represented in Chart 51, broken down by energy source.

Chart no. 51 – Installed electricity power of companies included in the NFS divided by energy source (MW) (2023)

Chart 51


In 2023, total gross energy production increased by 10%, going from 851 GWh in 2022186 to 933 GWh in 2023 (1,047 GWh, including energy produced by the photovoltaic plants of the subsidiary not consolidated on a line-by-line basis).

The increase was mainly attributable to higher rainfall during the year that impacted on hydroelectric energy production (+ 90 GWh, a 27% increase). There were also increases in photovoltaic (+7 GWh) and biogas production (approx. 6 GWh more), also due to the entry of Ecologica Sangro in the reporting scope187. For further details, see the Environmental Accounts.

Electricity generated from renewable sources, amounting to approximately 643 GWh (757 GWh including the photovoltaic plants of the subsidiary not consolidated on a line-by-line basis) represents the majority at around 69%188, with the following contributions:

  • 425.1 GWh from hydroelectric power,
  • 147.3 GWh from waste-to-energy,
  • 50,1 GWh from biogas (Orvieto Ambiente waste-management plants, Deco and Ecologica Sangro189, Aprilia and Monterotondo Marittimo sites of Acea Ambiente),
  • 20.4 GWh from photovoltaic plants190 (134.4 GWh including the plants of the subsidiary not consolidated on a line-by-line basis), see Chart no. 52 and Table no. 55.

In 2023, the upgrading and energy eciency measures at hydro- electric power plants continued, with the aim of optimising the use of available water resources, with the same specifications in terms of installed power and authorised by concession.

Almost half of the energy from waste-to-energy production is asso- ciated with the combustion of the biodegradable fraction of waste used as a primary source. In particular, the renewable share of the fuel (CSS) entering the San Vittore del Lazio plant, in 2023 was at around 47% of the total waste-to-energy production, whereas at the Terni plant, this share was at about 44%.

Chart no. 52 – Electricity produced subdivided by primary energy source (TJ) (2023)

Chart 52

Note: the values reported in the chart are expressed in TJ (1 GWh=3.6TJ).

Table no. 55 – Electricity produced (by primary energy source) (2021-2023)

primary energy source 2021 2022 2023

(GWh) (*)


diesel fuel







natural gas (co-generation)







waste-to-energy (approximately 55% of the total in 2022)







total thermoelectric














waste-to-energy (approximately 45% of the total in 2022)














photovoltaic solar (**)







total renewables







general total







(*) 1 GWh = 3.6 TJ.
(**) Some data from 2022 was adjusted following the consolidation, to also take into consideration the biogas production at the Ecologica Sangro site. Natural gas includes production by Ecogena.
(**) Photovoltaic includes the production at the plants located on Acea Ato 2 sites and in Orvieto, for a total of 2 GWh produced.
(****) Including the data from the photovoltaic plants of the subsidiary not consolidated on a line-by-line basis, the 2023 data would be solar photovoltaic 483.8 TJ (134.4 GWh), total renewables 2,724.9 TJ (756.9 GWh), overall total 3,770.5 TJ (1,047.4 GWh).


Total thermal energy produced in 2023 was 100.6 GWh.
The Tor di Valle thermoelectric power plant generated 83.9 GWh of thermal energy.
The heat generated was used to serve 41,385 residents in the area south of Rome (Mostacciano, Torrino and Mezzocammino) by means of a district-heating network which provides a volume equal to 3,716,272 cubic metres.

The thermal energy figure is supplemented by the 16,7 GWh of thermal energy produced in 2023 by the Ecogena plants.
The Ecogena plants also produced 11.6 GWh of refrigeration energy. For production data for the three-year period for Acea Produzione and Ecogena, see Products in the Energy business of the Environmental Report.

180 In particular, this refers to AE Sun Capital Srl, established in January 2022, and 40% owned by Acea Produzione and 60% by the investment fund Equitix Investment Management.
181 The power station is operational only in the event of extraordinary energy demand, and operation canal so be managed remotely from the control room at theTordiVallePower Station.
182 Output of the Acea Produzione, Acea Solar, Acea Renewable, SF Island and Fergas Solar 2 plants.
183 Includes the three lines of the San Vittore del Lazio plant and the power from the Terni plant. The figure has been adjusted in relation to what was previously published.
184 Cogeneration, i.e. the combined production of electrical and thermal energy, allows high eciencies to be achieved, between 80 and 90%. Trigeneration, which is a special application of cogeneration, allows use of a part of the thermal energy recovered in order to produce cooling energy in the form of cooled water for air conditioning in rooms or for industrial processes.
185 Total installed power includes the plants operated by Acea Produzione, Ecogena,Orvieto Ambiente, Acea Ambiente (waste-to-energy plants and the Aprilia, Monterotondo Marittimo and Grasciano 2 plants) and Deco for the production of biogas.
186 The data includes production by Ecogena.
187 Detailed information is provided in the Environmental Report: data for the Ecologica Sangro plant is also included for 2022, for comparison purposes over the two-year period. Excluding this contribution, the increase stands at 8% thanks to the rise in biogas production at the Orvieto Ambiente plant.
188 72% if including the photovoltaic plants of the subsidiary not consolidated on a line-by-line basis. 189 10.8 Gwh were produced from the Ecologica Sangro plants.
190 Detailed information is provided in the Environmental Report.