Self-consumption in brief
A brief semantic point
The terms sound alike, are often confused and yet don't mean the same thing. What do we mean when we talk about self-consumption?
Self-generation : local production, for own consumption or not. The self-generation rate is 100% if the installation covers all the site's consumption. It decreases if the production only offsets part of the site's consumption.
Self-consumption : you consume your own production. The self-consumption rate is 100% if all the electricity produced is consumed. When production exceeds consumption, the installation is oversized and the self-consumption rate falls.
To resell the entire production, you need to sign a contract with EDF Option d'Achat.
Two self-consumption configurations
- The producer is the sole consumer of the electricity produced on his site: individual self-consumption.
- Several producers and/or end consumers share the electricity generated on one or more sites: collective self-consumption. Production can be shared between residents of a building, or between different producer/beneficiary buildings in a district.
The production of electricity from renewable energies is, by nature, intermittent. This translates into periods without production, for example when there is no wind for a wind turbine, or no sun for a solar panel. Taking intermittence into account is essential when designing a self-consumption project.
In fact, a power plant's smoothed annual output can cover a building's year-round consumption; but on a one-off basis, the generating capacity may exceed the building's needs. As a result, there is a production surplus.
Collective self-consumption is an interesting solution when the plant is oversized and the producer's self-consumption rate is low. In particular, it makes it possible to dispense with less profitable or more technically complex solutions, such as surplus resale or storage (detailed below).
Support for self-consumption installations
Since 2016, an ordinance relating to the Law on Energy Transition and Green Growth has specified the framework for self-consumption.
The regulations commit grid operators and balance responsible parties to a voluntary approach to encourage the deployment of self-consumption operations. In particular, a number of economic advantages are granted to those involved in self-consumption projects throughout the production chain.
A bonus for self-consumption
It is awarded for the installation of a non-polluting and abundant means of energy production, contributing to the energy transition. It is a degressive and variable bonus, paid for investment in self-consumption projects.
- Installed directly on a roof;
- Have a peak power less than or equal to 100 kWp;
- Have been carried out by an installer who is a "Reconnu Garant de l'Environnement" (recognized environmental guarantor);
- The application for an Obligation d'achat contract must be made before the plant begins operation.
To obtain it, you need to apply to the grid operator and sign a surplus buy-back contract before the plant starts operating. The amount of the premium is calculated according to the tariffs set by a decree issued by the Commission de Régulation de l'Energie (CRE). The decree is revised every 3 months and depends on the renewable energy used (solar, biomass, biogas, geothermal, etc.). Payment is spread over the first 5 years of operation.
Investment premium rates for self-consumption installations with surplus resale
These data correspond to the prices set by CRE for a connection request for solar photovoltaic panels made between February and April 2023.
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What happens if production exceeds consumption?
If production exceeds the electricity requirements of the equipped building, it is possible to :
Storing excess electricity for later reuse
Resell and reinject surplus electricity into the distribution grid
There are several ways of storing the surplus electricity supplied by the power plant. In each case, the electricity is converted into another form of energy, before being returned in a smaller quantity. This is called yield.
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Each of these solutions has its advantages and disadvantages: some require major infrastructures, while others require the extraction of polluting materials whose recyclability is not guaranteed. Batteries, for example, are more efficient than STEPs for generating electricity quickly, but have a much lower storage capacity.
Storage is particularly interesting for sites that are isolated from the grid and need to ensure continuous electricity consumption. Storing electricity implies an additional cost for a project, and requires a detailed analysis of the match between the site's production and storage resources. It's an additional guarantee of autonomy that comes at both an economic and environmental cost.
It should be noted that many innovations are being developed in storage, which promises to be one of the challenges of the energy transition.
Resale and reinjection of surplus into the grid
The surplus is managed by a balance manager.
The Balance Responsible Entity is an operator who has signed a contract with RTE, the operator of the public electricity transmission network. Its role is to finance the difference between injections and extractions within a given balance perimeter. The quantity of electricity injected into the network must be equal to the quantity withdrawn. RTE ensures that this balance is maintained in real time.
- En cas d’écart négatif (injection < soutirage) : le responsable d’équilibre paie le financement du coût de l’écart. Le prix est fixé par RTE.
- In the event of a positive imbalance (injection > extraction) : RTE pays financial compensation to the Balance Responsible Entity.
Surplus production can be automatically allocated to a balance perimeter to compensate for any losses on the distribution network.
The balance responsible party proposes a feed-in tariff when the contract is signed. The amount paid depends on the plant's output. Re-injection can take place without financial compensation if the plant is less than or equal to 3 kWp.
Setting up a self-consumption system
Choosing the right renewable energy
The renewable energy source should be selected according to :
- Geographical area of installation ;
- Available space;
- The project owner's financial resources ;
- Electricity requirements of the site to be equipped.
Combining two energy sources, such as wind and solar, reduces intermittency and ensures stable, continuous production throughout the day and year.
Preparing the installation
As mentioned above, the installation must be sized according to the electricity consumption of the building to be equipped. Knowing your site's consumption (year-on-year, month-by-month, hour-by-hour) enables you to define the building's consumption heel (and therefore the optimum production to reduce surplus or storage needs).
The second step is to study the site's production potential. For WindBoxes, you can find out how to study the wind and solar potential here !
Lastly, depending on the type of self-consumption project, a number of administrative formalities need to be carried out (prior declaration before work, declaration of self-consumption, contracting with a balance responsible party, etc.).
Self-consumption, whether individual or collective, is a real lever of energy and ecological transition for buildings all over the world.
By offering greaterenergy autonomy to equipped sites, self-consumption helps to reduce annual bills and ensure the long-term viability of the business by securing the supply of local renewable electricity.
To be put to good use, a solar, wind or hybrid power generation system needs to be correctly sized. The preparatory phases of measurement, analysis and potential study are the keys to the success of a self-consumption project.
Depending on the size of the installation, there are three options open to the project owner: resell the entire production, consume all the electricity if the building's needs allow, or consume part of the production and resell and reinject the surplus into the national grid. In the last two cases, the installation carried out will be eligible for the investment bonus (if the peak power is less than 100 kWp), an initiative pushed by the government to accelerate the deployment of self-consumption projects since 2016.
Self-consumption of renewable energies ultimately brings consumers closer to producers and increases their energy autonomy, with minimal environmental impact and long-term economic benefits.