Which photovoltaic systems are worthwhile?

By Spare Wheel, 10 July, 2021

Researchers have published current studies on the profitability of private photovoltaic systems. The main result is that the size of the system and the availability of an electricity storage system can influence the level of return, but that almost every system pays off.

Researchers, in particular, have been warned in recent years that private photovoltaic systems are no longer profitable in many cases. The fact that it comes to different results today is essentially due to the lower purchase prices. In 2017 alone, the acquisition costs for a photovoltaic system have dropped by more than 3%. Since the feed-in tariff was not reduced any further, even feeding in solar power is now profitable again. The yield that can be achieved is not great, but electricity generation costs of between eleven and twelve cents per kilowatt-hour are offset by 12.2 cents. Anyone who consumes all of the electricity and completely avoids self-consumption can still expect small returns of around 1%.

According to researchers, yields of between 5.6 and 8.0% are typically achieved with a roof system without electricity storage. Here, a self-consumption of 25 per cent is assumed. In addition, average solar radiation is assumed. At particularly favourable locations and with a particularly favourable south orientation of the roof, even a double-digit return can be achieved. As a prime example, a system with a nominal output of six kilowatts was examined, for which acquisition costs of 7800 euros were assumed.

The researchers came to different results for photovoltaic (PV) systems with electricity storage. Although these investments also pay off, the average returns are significantly lower at 1.9 to 3.6%. It should be noted, however, that the company does not include funding for battery storage in its invoice. This could hardly be implemented in general sample calculations. The funding for battery storage is tied to numerous conditions. In addition, some federal states have set up their support programs for storage. If a subsidy was possible, system operators could expect higher returns than 3.6%.

In another example, researchers looked at a five-kilowatt system with a purchase price of just 7,000 euros. Once again, a self-consumption of 25% is assumed. A purchase price of 26 cents per kilowatt-hour is assumed for the electricity saved in this way. (Correctly, only the consumption-dependent portion of the electricity costs is taken into account here. The non-consumption-dependent basic fee is not taken into account.) In 20 years, self-consumption will most likely amount to 23,500 kilowatt-hours (corresponds to 6110 euros), while the economy will consume 70,500 kilowatt-hours (corresponds to 8601 euros). The total financial return of 6100 + 8600 = 14710 euros is offset by the acquisition costs of 7000 euros and estimated operating costs of 120 euros per year, i.e. a total of 2400 euros. So there remains a surplus of 5300 euros. It is noteworthy that this calculation results in a positive return even without assuming any future electricity price increases.

Similar sample calculations are published regularly. It is obvious that the higher the proportion of self-consumption, the higher the return on a system. In recent years, this has meant that private system buyers have tended to opt for smaller systems to achieve higher self-consumption. However, the impact on the return is minor because the acquisition costs per kilowatt are higher for smaller systems.

Photovoltaics pays off

To summarize, according to the calculations of the company, a photovoltaic roof system almost always pays for itself. Whether an additional electricity storage system pays off depends on the funding available. However, every configuration promises a higher return than fixed-term deposits.