On grid, off grid or hybrid photovoltaic installations? The most important differences

When deciding on such a long-term investment as a photovoltaic installation, the types of systems available on the market should be thoroughly analyzed by us. The target profitability and effectiveness of the entire project will depend on which of the solutions we choose now. In order to facilitate this process for all interested parties, below we present a summary of the most important information on the specifics of the three main types of PV systems – off grid, on grid, and also hybrid.

In terms of a photovoltaic installation, the types of connections are one of the most basic criteria used to classify its particular types. Based on such a system of division, the following installations can be distinguished:

• connected to the network, without its own batteries,
• not connected to the network and taking into account their own batteries,
• not connected to the network and taking into account their own batteries,
• Each of them is described in a bit more detail later in the post.

On grid installation – with access to the network

As for the types of photovoltaic installations, their name in itself is a good indication of their specificity. Following this lead, in this case it is easy to say that on-grid systems will be connected to the power grids, thanks to which all excess electricity generated by them is transferred to it on an ongoing basis. In such a situation, the energy exported to the network owned by a specific plant can be sold or stored, and then 80% of it can be collected in the future, when the installation will not be able to cover the required energy demand (the mentioned circumstances may take place in particular during the autumn and winter period).

In addition to the previously described feature, a networked PV system also has the advantage that it does not require batteries for its operation, which usually significantly increase the costs of the entire investment. For this reason, one of the most frequently chosen solutions, both among institutional and private investors interested in photovoltaics, is the on grid installation.

On the other hand, this feature also raises a problem – we are still dependent on the local electricity supplier. In the event of a failure of the power grid to which the system is connected, it will not be able to operate at all, because for safety reasons, its operation will be automatically stopped by the inverter. For people expecting complete independence from an external energy company, a better, though more expensive option than the on-grid installation will be its island or hybrid counterparts, described in more detail later in the post.

Off grid installation (island) – with no access to the network

As you can easily guess at this stage of the article, an off-grid installation – also known as an island system – is a variant of the PV system operating independently, without connection to the local power grid. In order for unused energy to be stored on an ongoing basis, its design should take into account dedicated batteries.

For this type of solution, there are two requirements that are necessary to meet the full functionality of the solution. The first one is a sufficiently large potential in terms of the amount of generated electricity, while the second one is adequately capacious batteries that enable the storage of the entire surplus produced energy. It should be remembered that the off grid installation, like any other installation, works much more efficiently during the warm months of the year. In the absence of access to the local power grid, the entire system must therefore be designed in such a way as to replenish the shortages of electricity in autumn and winter based on the reserves stored in the batteries in spring and summer.

As for the types of photovoltaic installations used in Poland, due to the previously described state of affairs, high battery prices and the need to regularly replace them (on average once every 400 full cycles), island systems are a rather rarely chosen solution. They can be found primarily as part of summer cottages or tourist boats or cars.

Hybrid photovoltaic installation – combining the advantages of both previous solutions

Hybrid photovoltaic installation combines the types of systems described earlier into one comprehensive solution. On the one hand, it offers the possibility of storing energy inside the batteries, and on the other hand, it still leaves the option of obtaining or transferring electricity to the external network to which it is connected.

In addition, a hybrid photovoltaic installation provides another interesting advantage, allowing you to charge the batteries not only with self-generated energy, but also with that from a local supplier. Assuming that we use this option as part of a low tariff (usually in the 22:00 – 6:00 hours), we will get additional savings during months with little amount of sunshine.

At the moment, the only factor discouraging people interested in photovoltaics from choosing this system are the relatively high prices of batteries and their consumption, but it must be mentioned here that over time these parameters are increasingly optimized by producers. It is possible that soon it is the hybrid photovoltaic installation that will become the most frequently chosen option among Polish investors.