More and more homeowners have photovoltaic systems on their roof. Halfpoint Images/Getty Images
Solar energy is booming. And more and more German homeowners are having a photovoltaic system built on the roof.
The self-sufficiency calculator from the University of Applied Sciences in Berlin gives an impression of how much electricity can actually be saved.
In this way, an average family household of four can make itself independent of the electricity provider by around 72 percent. Including the feed-in tariff, this corresponds to savings of a good 1400 euros per year at current electricity prices.
The expansion of solar energy in Germany is booming. The three millionth photovoltaic system was recently reported to the Federal Network Agency. From January to March of this year, homeowners installed twice as many solar systems as in the first quarter of 2022, according to the German Solar Industry Association. But how much electricity does the system really save? And how high is the electricity price in the end?
Solar system: Just two kilowatts of nominal power bring 23 percent self-sufficiency
Different computers from the HTW Berlin and the consumer advice center NRW give an impression of this. First of all, it should be said: The actual yield of each solar system depends on many individual factors. Of course, this includes which system is installed on the roof and the actual hours of sunshine at the respective installation site. However, the orientation of the roof surfaces and the angle at which the solar panels are set up can also influence electricity production. And when you turn on large appliances like washing machines, affects how much of the electricity produced you use yourself – and thus the overall savings.
Let’s take a four-person household as a reference. According to the comparison portals Check24 and Verivox, it has an average annual power consumption of 4250 kilowatt hours. The self-sufficiency calculator of the HTW Berlin now allows an insight into what proportion of the electricity can be fed from solar energy in the future, depending on the size of the system.
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It is noticeable: A larger one solar system alone does not necessarily mean more independence. In the case of smaller systems with less maximum output, the proportion that the owners themselves consume is higher in percentage terms. The measure of maximum power is kilowatts, often referred to as kilowatt peak for short. It indicates how much electrical power solar cells can deliver under standard conditions.
Example: A system with a two-kilowatt peak without storage leads to a degree of self-sufficiency of 23 percent. This means: 23 percent or 977.5 kilowatt hours per year come from in-house production. With the average electricity price of around 28.3 cents according to Verivox, this would correspond to annual savings of 227.80 euros.
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In a system with a five-kilowatt peak, the degree of self-sufficiency increases to 32 percent. That corresponds to 1360 kilowatt hours of electricity or 384.88 euros. At ten kilowatt peak, the degree of self-sufficiency increases by only five percent to 37 percent, or 1572.5 kilowatt hours and around 445 euros. The reason: Only a small part of the electricity produced is consumed by the company itself, the rest is fed into the grid. But: For the rest of the approximately 10,000 kilowatt hours that are fed into the grid, there is a feed-in tariff of around 645 euros per year.
It should be borne in mind that the price of electricity could rise in the long term. There are of course no exact forecasts due to many imponderables. Experts from the consulting firm Prognos, for example, reckoned with an increase of 50 percent in wholesale by 2030 in 2021 – i.e. before the energy crisis. A forecast by EWI Cologne had shown how unreliable such forecasts are. Its forecast from 2018 was already torn in 2021 – instead of in 2030 as planned. However, if you believe these surveys, every self-produced kilowatt hour should become more valuable in the long run.
The power storage makes the difference with solar energy
The computer shows that an electricity storage system is a good way to increase self-consumption. A consumed kilowatt hour is already more valuable than the kilowatt hour fed into the grid. Because while you currently pay an average of 28.3 cents per kilowatt hour from your electricity provider, you only get 8.2 cents as compensation for each one you feed into the grid.
If you add a storage system with a capacity of six kilowatt hours to your system with a nominal output of ten kilowatts, you will achieve a degree of self-sufficiency of 72 percent, according to HTW Berlin. Around 3060 kilowatt hours come from in-house production. Your electricity bill from the provider is currently reduced by around 880 euros.
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In addition, there is a feed-in tariff of around 550 euros per year. All in all, you are currently saving around 1430 euros a year. With a degree of independence of 72 percent, you also make yourself less dependent on any rising electricity prices.