Europe — Use cases
Energy community modelling for European projects
The EU's Renewable Energy Directive (RED II) created the Renewable Energy Community (REC) and Citizen Energy Community (CEC) frameworks, which member states are transposing in distinct ways. Italy's CER, Spain's autoconsumo colectivo, France's autoconsommation collective, and Germany's Mieterstrom and Energy Sharing each create different modelling requirements. HOMER Pro and HOMER Grid handle all four.
CEC vs REC: the EU framework
The EU's Electricity Directive (2019/944) created the Citizen Energy Community (CEC) — a broad framework for collective energy activities by citizens and small businesses. The Renewable Energy Directive II (2018/2001, as amended 2023) created the Renewable Energy Community (REC) — specifically for communities whose primary purpose is providing environmental or economic benefits to their members. Both share the same basic economic model: shared generation, collective consumption, and mutual allocation of energy flows — but their eligibility criteria, geographic constraints, and incentive structures differ.
Member states have transposed these directives with significant variation. Italy went furthest and fastest, with DM 7/12/2023 establishing explicit incentive levels. Spain's RD 244/2019 predates RED II but aligns with it. France's Loi APER 2023 substantially expanded the geographic perimeter. Germany's Solarpaket I 2024 introduced Energy Sharing provisions for the first time. HOMER Pro and HOMER Grid model energy community economics across all four national frameworks.
Italy — Comunità Energetiche Rinnovabili (CER)
Italy overview →Italy's CER framework under D.Lgs 199/2021, implemented by DM 7/12/2023, is the most detailed energy community framework in Europe. Key parameters:
Geographic scope
Members must share the same Terna primary substation (cabina primaria) service area. Terna publishes the perimeter maps. No fixed distance limit — defined by network topology.
GSE incentive
Up to €110/MWh on shared energy (virtualmente condivisa) — the portion of generation matched against member consumption in the same hour. Enhanced supplement for storage-enabled CERs.
Eligible participants
Households, SMEs, public bodies, local authorities. Large enterprises excluded from being members (but can host generation). No prosumer size limit for generation.
Storage role
BESS within the CER perimeter is explicitly incentivised. Storage increases the shared energy fraction, thereby increasing the total GSE incentive. HOMER Pro models the optimal storage sizing for Italian CERs.
Spain — Autoconsumo colectivo
Spain overview →Spain's autoconsumo colectivo framework under RD 244/2019 permits groups of consumers connected to the same low-voltage network — within a 2 km geographic perimeter — to share a single generation installation. Unlike the Italian CER, Spain's framework focuses primarily on the avoided grid import and the net-billing surplus compensation rather than an explicit shared-energy incentive.
2 km geographic rule
Participants in an autoconsumo colectivo arrangement must be within 2 km of the shared generation installation, measured at the nearest grid injection point.
Net billing and surplus compensation
Shared generation reduces individual participants' grid imports. Surplus exported to the grid is compensated at the OMIE spot price. No additional incentive above the avoided cost of grid import.
France — Autoconsommation collective
France overview →France's autoconsommation collective framework, significantly expanded by Loi APER (2023), allows groups of consumers and producers to share electricity within a geographic perimeter defined at the transformer level. Loi APER extended the permissible rural perimeter to 20 km — from the previous 2 km limit — and created zones d'accélération to fast-track renewable development in rural areas.
Urban vs rural perimeter
Urban: 2 km at LV/HTA transformer. Rural: 20 km under Loi APER 2023. French models require explicit geographic mapping of the transformer perimeter to define eligible participants.
Allocation coefficients
CRE approves the allocation key for distributing shared energy among participants. Fixed or dynamic keys permitted. HOMER Grid models both allocation approaches.
Germany — Mieterstrom and Energy Sharing
Germany overview →Germany has two distinct collective consumption frameworks with different economic structures. Mieterstrom (tenant electricity) under §42b EnWG allows building owners to supply rooftop solar to residential tenants at below-retail rates, receiving a Mieterstrom Zuschlag (supplement) above the feed-in tariff. Energy Sharing under Solarpaket I 2024 is a broader framework allowing collective consumption across a wider geographic area, more aligned with the REC concept.
Mieterstrom Zuschlag
Supplement above the EEG feed-in tariff for electricity supplied to residential tenants. Up to €3.8/kWh (2024). Building boundary rule — generation and consumption must be in the same building or adjacent building.
Energy Sharing (Solarpaket I)
Permits shared consumption from a common generation source across a broader geographic area than Mieterstrom. Similar to the REC model. Full implementation framework still evolving as of 2024.
HOMER Pro and HOMER Grid for energy communities
HOMER Pro models energy community configurations with multiple generation points, multiple storage assets, and heterogeneous load profiles. The multi-party economic model allocates generation, storage, and grid costs among participants according to the applicable national allocation rules — whether Italian GSE coefficients, Spanish static allocation, French CRE-approved keys, or German Mieterstrom building-level accounting.
HOMER Grid handles the simpler two-party or small-group configurations common in commercial self-consumption arrangements — behind-the-meter at a single site, or a rooftop PPA arrangement between a building owner and one commercial tenant. For larger, multi-member communities with complex allocation rules, HOMER Pro provides the additional granularity required.