Zero feed-in: When the photovoltaic system does not feed any electricity into the public grid
Anyone thinking about electricity from solar energy or setting up their own photovoltaic system will sooner or later come into contact with feeding electricity into the public grid. The term “zero feed-in” also comes up. This article explains what this is all about.
How a photovoltaic system works
In order to clarify the question of zero feed-in, it is first important to understand how a photovoltaic system works and how the solar power generated can be used. In a photovoltaic system without battery storage, the electricity must be consumed when it is generated. This applies to both private households and factories or industrial companies. This means that the electricity is either consumed in your own home or business or fed into the public grid.
Every kilowatt hour of electricity from your own photovoltaic system reduces your electricity bill, as you do not have to buy electricity from the public grid. It is also possible to feed surplus electricity into the public grid. This fed-in electricity is subject to the so-called feed-in tariff, which is regulated in the Renewable Energy Sources Act (EEG). The law determines how many cents are paid per kilowatt hour fed into the grid. While feeding electricity into the grid from photovoltaic systems used to be a lucrative business, feed-in tariffs have fallen continuously in recent years. While the remuneration at the turn of the millennium was still just under 50 cents per kilowatt hour, today it is usually less than 10 cents. The most profitable option today is therefore to use the electricity from a photovoltaic system yourself.
Zero feed-in in detail
While photovoltaic systems were mainly installed in Germany in the early years to feed electricity into the public grid, the focus today is on self-consumption. As a result, more and more systems are being commissioned with the option of zero feed-in. Zero feed-in means that no energy from your own photovoltaic system is fed into the public grid. This requires special hardware that prevents the inverter from feeding energy into the grid when it is not needed in your own system.
But what happens to the surplus energy? Anyone pursuing the zero feed-in strategy has installed an additional electricity storage unit, for example. The surplus energy flows into this storage unit and is stored there until it is needed again. Whether this is for charging electric vehicles, for trading on the electricity market or as a reserve for backup power supply is up to the operator.
Alternatives to zero feed-in: full feed-in and surplus feed-in
With full feed-in, all the electricity from the photovoltaic system is fed directly into the electricity grid. This method was very popular in the boom times of solar energy, but is hardly profitable today as the feed-in tariffs have fallen significantly. Nowadays, most privately used photovoltaic systems utilise surplus feed-in, where only the surplus electricity is fed into the electricity grid.
For whom zero feed-in is worthwhile
The idea behind zero feed-in sounds logical: electricity that is not consumed directly is stored and used later. However, this strategy had a catch: in the past, energy storage solutions were relatively expensive. The purchase of a battery storage system and the associated savings in energy costs were not well balanced. As a result, the electricity was neither consumed, stored nor fed into the grid during zero feed-in – it was simply lost. However, this has changed in recent years: The cost of battery storage has fallen massively and the technology has developed rapidly.
The problem with buildings with large roof areas is often that the photovoltaic system generates considerable power in good weather, which is significantly higher than the self-consumption. In weak sunlight, however, the output is just sufficient to cover your own electricity requirements without having to purchase expensive grid electricity. What to do in such a case? Due to the high fluctuations, the grid operator may not authorise the feed-in. In this case, it makes sense to invest in an additional battery storage system. A solar system with zero feed-in can thus be a permanently profitable option and pay off in the long term.
The different forms of zero feed-in
There are different approaches to zero feed-in. Without storage, an inverter can adapt production to consumption by reducing production when consumption is low. This means that there is no surplus electricity.
The second variant is a photovoltaic system with a storage system. In this case, the surplus electricity is temporarily stored in a battery storage system. Commeo offers various storage solutions in different sizes – customisable to the respective requirements. Together with the intelligent Energy Control System including inverter, the system ensures that the electricity is stored in phases of overproduction. It monitors both the electricity demand, for example in the company, and the charge level in the battery storage system. As a rule, the electricity flows to the consumers first. If their demand is covered and surplus electricity is available, this flows into the energy storage system. When both the electricity demand in the company is covered and the battery storage system is fully charged, the photovoltaic system reduces power generation until there is demand again.
What are the requirements for zero feed-in?
In principle, zero feed-in is permitted for every photovoltaic system. The exact legal provisions on this are set out in Votum 2019/7 of the German Renewable Energy Sources Act (EEG). Of course, the system – like any other photovoltaic system in Germany – must be registered in the Federal Network Agency’s market master data register no later than one month after commissioning. The system must also be checked and approved by the grid operator. This is the only way the grid operator can ensure that the system is grid-compliant and authorise its operation.