Deep dive photovoltaics
Further Literature
*Some of the following developments were discussed in German language in the DIW Wochenbericht 33/2024 in more detail. However, the following data is more recent.
Global Development
No other electricity generation technology is currently growing as rapidly or attracting as much investment worldwide as solar photovoltaics (PV). The threshold of one terawatt (equivalent to one billion kilowatts) of globally installed capacity was already surpassed in 2022. By the end of 2024, this figure had reached around 1.9 terawatts, according to data from IRENA. While Europe — especially Germany — led in installed PV capacity until the mid-2010s, current growth is dominated by Asia, and in particular by China (figure above, left).
A comparison of installed PV capacity per person, based on data from IRENA and World Bank, clearly shows Germany's pioneering role at the beginning of the 2010s, but also a subsequent slump in expansion (figure above, right). In the 2020s, however, PV in Germany grew strongly again, most recently faster than ever before. In other countries, however, per capita growth was even faster. For example, the Netherlands has now overtaken Germany in terms of installed capacity per person and is only just behind Australia, which is very rich in sunshine. Belgium has also been able to increase its installed PV capacity very strongly in recent years. This means that the Netherlands, Germany and Belgium have installed more PV capacity per person than Spain, which has more sunshine. Even Poland, which is generally known for its coal-fired power generation, has recently seen such a strong increase in PV installations that it now has almost as much PV capacity per capita as Italy.
Installed Capacity
The following graph shows the development of installed PV capacity in Germany by installation type. Building PV systems (which are mostly rooftop installations) still make up the largest share of total capacity. Balcony power plants, due to their very small individual module capacities, account for only a very small portion of the overall installed capacity.
The following figure focuses on the segment of ground-mounted PV systems. It also shows an indicative target trajectory based on the Federal Government’s Photovoltaic Strategy, which assumes that half of future capacity additions will come from ground-mounted installations. Current developments fall significantly short of this target trajectory.
Net additions
... by installation type
Similar to the total portfolio shown above, the following figure shows the monthly net additions by type of system since 2017. The data basis for this is the Marktstammdatenregister (MaStR). In addition to the general upward trend, the figure shows that the expansion in almost all months was strongly driven by the building PV segment, which are predominantly rooftop systems. The figure also shows that the segment of small balcony/Plug-in PV systems has recently grown strongly, albeit from a very low level (double-click on the corresponding legend entry). It should be noted that only some of the balcony systems are likely to be correctly recorded in the market master data register.
The following figure additionally shows the share of total annual net additions by installation type since 2000. So far ground-mounted installation have never reached a share of 50% of total additions as envisioned by the Photovoltaic Strategy from 2026. In recent years, the share fluctuated around about one third.
... by installation size
The expansion can also be differentiated according to system size (select individual size classes by clicking on the legend). Ground-mounted systems have become increasingly larger in recent years. Systems with an output of at least five megawatts have recently accounted for the largest share of new installations.
In the case of building PV, smaller systems up to 25 kW accounted for the majority of monthly net additions in 2023 and 2024. These systems are likely to have been installed predominantly on the roofs of private households. However, the segment of larger and presumably mostly commercial building PV systems has recently grown significantly.
... by subsidy type
The German Network Agency provides data on net additions by subsidy type in the last twelve months. The following figure shows that the lion share of additions receive feed-in tariffs or premiums in accordance to the German Renewable Energy Sources Act. In most cases additions are small rooftop installations. Not even half as many additions receive subsidies resulting from a reverse auction, in which the lowest subsidy bids by installation owners win. Installations participating in these auctions are mostly large-scale ground-mounted plants. The share of installations not receiving any subsidies is rather small at this point. Such installations are e.g. marketed under power purchasing agreements (PPAs) or serve own consumption of larger industrial or commercial consumers. Lastly, this segment also includes some preliminary or unverified entries into the database. The Mieterstrom (tenant electricity) segment has been rather niche so far.
German state level
... installed capacity absolute and relative to potential
This section splits additions and installed capacity by German states. In the following figure, the left panel shows that Bavaria has the most installed capacity hosting roughly a third of all ground-mounted capacity. Far behind follow Baden-Württemberg, North Rhine-Westphalia, Lower Saxony und Brandenburg. Among these states only Brandenburg has a larger share of ground-mounted installations. The overall capacity in the city-states is negligible.
However, comparing absolute capacities is somewhat misleading as the states differ substantially in terms of landscape, building density and other factors that drive PV capacity potential. In order to admit a like-for-like comparison we express installed capacities as a share of the potential, as recently estimated by the Adriadne-Project, for each state by installation type. For the buildings segment there is not much variation across states. Consequently, large Bavarian capacities in this sector derive from a large potential. On the other hand, some states that seem to trail behind on an absolute basis actually use their potential similarly to states hosting much more capacity in absolute terms. Also in terms of use of potentials the city-states fall behind. Part of the reason is that they have historically faced issues in coordinating deployment for multi-family homes.
For ground-mounted installations, there is significantly more variation across states in terms of use of potential. While Saarland, Brandenburg and Bavaria are doing comparatively well, Baden-Württemberg, North Rhine-Westphalia and Lower Saxony have only used a fraction of their potential so far.
... installed capacity and trend as a share of potentials
The following maps show the installed capacity by German state as a share of their respective potential both for ground-mounted and building installations in the left panel. The right panel shows the net additions as a share of the potential for the last twelve months until the end of last month. It is clear that installed capacity and installation dynamics (measured in terms of additions in the last 12 months) correlate. Bayern and Saarland are in the lead here, while Thuringia and Saxony-Anhalt which have been slow to add capacity in the last twelve months have only used a small share of their overall capacity so far. City-states are far behind in terms of installed capacity. However, their trend places them better. Data for Bremen are rather unreliable as the estimated potential seems very small compared to recent additions.