Self-generation of energy with photovoltaics
Since January 2015, when the decision was signed for the self-production of energy with photovoltaics (net metering), the program known throughout the world as net metering, according to which photovoltaics are installed in a building, the production of which is deducted from the consumption of the user. Offsetting with self-production is energy (in kWh) and is done annually with a 25-year contract for it and is often called self-production of electricity with energy offsetting from photovoltaic systems.
What is net-metering?
The concept of self-production of energy with photovoltaics exists in many countries with the term net metering. In Greece, since October 2013, the possibility for self-production of energy or self-consumption or self-consumption of energy in every building (residential or business) using Renewable Energy Sources (PV, wind turbines) comes into force.
​
According to the Ministerial Decision on the self-production of electricity with energy compensation from photovoltaic systems of January 2015 a limit of 20kWp is set in all buildings (10kWp for non-interconnected Aegean islands) or half of the agreed power, thus opening the window for projects self-production of greater power.
​
A photovoltaic self-generation system can only use PV that will be installed on a tile roof, roof, ground, patio cover or any other legal structure.
​
Any home or business owner with a PPC meter in their name or a tenant of the space can install PV for self-production of energy with energy compensation from photovoltaic systems.
Each self-generation system must be assigned to a single meter, while more than one self-generation system can be installed in an apartment building. In case of installation of a system by one of the owners, written consent is required from the other owners.
​
Self-generated energy systems are interconnected with the public grid (PPC) systems in which energy netting of produced and consumed energy is done (as opposed to the well-known interconnected PV with tariffs in which accounting netting is done in euros).
​
In simple words, the self-producer of electricity with photovoltaics produces the energy he needs with the help of photovoltaics and consumes it directly in his building at the same time. The building remains interconnected with the public electricity network. When it does not have enough energy, instead of having accumulators, as with an autonomous photovoltaic system, it takes from the grid.
​
In the case of photovoltaics for self-production, the excess energy during the day is channeled to the PPC and the consumer essentially "takes it back" during the evening or when it is needed within a year.
​
In this way, the cost of batteries (the most perishable part of an autonomous photovoltaic) is avoided, which is the part of an autonomous system that needs replacement faster and has huge costs.
​
The calculation of the size and composition of a self-generated power system with photovoltaics is done with a simple method based on the recording of the needs of the building and is briefly presented in the section Self-producer calculation with photovoltaics.
​
The measurement will be done with a two-way meter as until now with the domestic interconnected solar panels. The user, for example, in one year will have consumed 4000kWh and the self-generated PV will have produced 3000kWh. In this case, the consumer will pay the difference between the two meters, i.e. 1000kWh.
A self-generated PV is built like an interconnected PV. It consists of the PV panels that produce direct voltage and an inverter that converts the voltage into alternating current ready for use.
​
The self-production of electricity with photovoltaics is the best solution for eliminating electricity costs for households and businesses, while it can also eliminate heating-air conditioning costs if properly combined with a heat pump, for example.