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Self-production in Domestic buildings

1.Net -Billing

Net-Billing is the new regulatory framework for energy self-consumption. It allows residential consumers to use the energy generated by their photovoltaic systems in real-time and sell any surplus energy. The maximum power capacity for single-phase systems is 5 kW, while for three-phase systems, it is 10.8 kW.

"Photovoltaic Net-Billing systems are connected to the grid, and when the energy produced by the system is insufficient to meet the self-consumer’s needs, energy is drawn from the grid. The self-consumer is charged the applicable energy price for that period. For surplus energy sales, household self-consumers may be represented by the Renewable Energy Sources Operator & Guarantees of Origin (DAPEEP) and receive compensation based on the energy injected into the grid, calculated using the wholesale market clearing price at the time of injection. Specifically, using the metering data from the Operator, DAPEEP calculates the monetary value of the injected energy per Deviation Clearing Period based on market participation revenue. Monthly, DAPEEP pays the supplier the monetary value of the total injected energy, aggregated for the month, and the supplier issues the self-consumer’s electricity consumption settlement bills."

Net-Billing systems can be installed by property owners with an active permanent power supply. Photovoltaic power plants can be installed on buildings, on the ground, or on other structures, as long as they are located on the same or adjacent property as the consumption facility. Alternatively, they can be situated in a separate location, provided they are electrically connected to the consumption facility via a dedicated interconnection line.

Net-Billing PV systems can also be paired with storage solutions to maximize self-consumption and reduce dependence on energy cost fluctuations, while still allowing the sale of surplus energy. Specifically, when energy production exceeds consumption, surplus energy is stored in batteries. If energy production falls short of the required demand or is zero, the stored energy is used to meet the home’s energy needs.

Advantages of Net-Billing:

  • Quick return on investment
  • Lower energy costs
  • Renewable energy production with reduced carbon dioxide emissions
  • Protection from electricity price fluctuations
  • Tax-exempt compensation

Differences Between Net-Metering and Net-Billing:

  • In Net-Metering, the excess energy injected into the grid is offset against the energy the self-consumer draws from the grid. In Net-Billing, the self-consumer is compensated for the energy injected into the grid at the wholesale market clearing price at the time of injection.
  • Net-Metering is available only to specific groups, including registered farmers, agricultural holdings with farm use benefits, first- and second-degree local authorities (which are bodies of the General Government), and vulnerable households. Net-Billing, on the other hand, is available to any legal or natural person.
  • The billing methods differ between the two systems: Net-Metering offsets energy usage, while Net-Billing compensates based on the energy injected into the grid.
  • The connection contract with the Grid Operator for Net-Billing photovoltaic systems is valid for 20 years, while for Net-Metering systems, the contract duration is 25 years.
  • Net-Billing allows self-consumption in multi-family buildings (collective self-consumption), which is not permitted under Net-Metering.
  • Net-Billing allows the installation of photovoltaic systems at secondary residences and enables energy synchronization from multiple consumption sites (e.g., a main residence or office) that are not located on the same or adjacent premises and are not connected by a dedicated interconnection line (virtual Net-Billing). However, all facilities must be registered under the same Tax Identification Number (TIN).

The equipment required to install a Net-Billing system is the same as for Net-Metering.

2. Virtual Net-Billing

Virtual Net-Billing allows consumers to locate their photovoltaic production plant in a different area from their consumption facilities, as long as all the facilities are registered under the same natural person (i.e., the same VAT number). Photovoltaic power plants can be installed anywhere in the country, regardless of the location of the consumption facilities being offset, as long as both the power plant and the consumption facilities are within the same electricity system—either the interconnected grid or, for non-interconnected islands, the respective regional grid. The consumption facilities to be offset must not be electrically connected to the generating station’s internal electrical system, even if they are on the same or adjacent site. The energy produced by the photovoltaic plant is fed into the grid and offset in real-time against the energy consumption at the user’s premises. This is done using smart meters, which compare the installation’s consumption with the photovoltaic plant's production in 15-minute intervals.

Under the new legislative framework, self-consumers are now able to collaborate in apartment buildings through Collective Self-Consumption. This is possible when at least two supplies are located within the same building and wish to jointly install photovoltaic systems, while sharing the energy produced among themselves. The energy sharing is subject to applicable network charges, fees, levies, and taxes. Additionally, public utility consumption can be included in the collective self-consumption scheme. The photovoltaic power plant may either be owned jointly by the self-consumers or managed by a third party, provided the third party remains under the control of the self-consumers. The photovoltaic system will be connected to the grid or the system via a new consumption supply, and the virtual Net-Billing procedure will apply proportionally.

3. Zero Feed-In

The rapid growth of renewable energy, particularly photovoltaic systems, has led to grid saturation, where, at certain times, the energy produced exceeds consumer demand, and the grid is unable to accommodate the surplus. Zero Feed-In systems address this issue by ensuring that energy produced is used exclusively for the self-consumer's own consumption, with no excess energy being fed into the grid. This makes it possible to connect a photovoltaic system to a saturated grid, provided that the saturation is due to exceeding the rated capacity of the grid components or surpassing the voltage limits at grid nodes.

The setup of a Zero Feed-In self-consumption system is similar to that of a Net-Billing or Net-Metering system, with the key difference being the inclusion of an energy analyzer. This device ensures that no energy is injected into the grid, effectively preventing grid overload.

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