Solar system with storage pays for itself within ten years

20.05.2025

Source: E & M powernews

Extensive in-house power supply can pay off for companies. Initial investments in the millions are recouped within a decade, as the example of a furniture store shows.

Electricity from in-house production, combined with an energy storage system - this promises companies extensive independence from fluctuations in electricity prices. The "opportunities for trade and industry" offered by green energies have now been discussed at an event organized by the South Westphalia Regional Association of the NRW Renewable Energies Association (LEE NRW).

At the conference venue in Arnsberg on May 20, the solar system manufacturer Entegro Photovoltaik-Systeme GmbH presented the genesis of a system including storage, which the furniture store Ostermann will have installed at its Witten site in the Ruhr region from August. According to Entegro Managing Director Dieter Röttger, the money invested in the chosen configuration can be amortized in less than a decade.

The Fröndenberg-based company provides its customers with comprehensive advice, including the calculation of various system sizes. Annual consumption in Witten is around 2.7 million kWh. Ostermann ultimately opted for a ground-mounted system on its own premises, which has an output of a good 1.3 MW. This alone would ensure a degree of self-sufficiency of 42 percent, with 61 percent self-consumption of the electricity generated.

Entegro builds solar plant for furniture store Ostermann in Witten

The question of own use and/or feed-in of the electricity generated is a tricky calculation. After all, a solar power plant does not always produce electricity when the furniture store needs it.

Entegro CEO Röttger outlined the advantages of putting the resulting plant into operation in certain phases and aligning the potential funding from the Renewable Energy Sources Act (EEG) accordingly. For Witten, it would be possible to consume non-subsidized electricity on the one hand and to feed in part of the plant's production and thus take advantage of the market premium on the other. The choice of feeding in as a priority and consuming as a secondary priority could be made at will.

In total, the investment of 1.235 million euros in the plant would be recouped after 5.9 years. On the one hand, this would result in savings of a good 204,000 euros per year by avoiding (expensive) electricity purchased from the grid. And on the other hand, there is an annual remuneration of 24,000 euros for the energy fed into the grid.

This balance can be further improved with an energy storage system. The battery cells embedded in 20 containers (total capacity 3,500 kWh) can absorb surplus solar power and increase self-sufficiency during periods of low sunshine. According to Dieter Röttger, this increases the self-sufficiency of the power supply to 57.2 percent and the self-consumption of the electricity generated to 86.9 percent.

This results in initial expenditure of 672,000 euros. At the same time, the storage system allows an additional 440,000 kWh of electricity to be used each year. This avoids annual electricity costs of around 85,000 euros. After deducting the annual maintenance costs of 8,500 euros, Ostermann in Witten has a cost advantage of a good 73,000 euros. This means that the initial expenditure would be balanced out after eight to nine years.

From the kebab store next door to the company's mainstay in Turkey

As Röttger from Entegro went on to explain, companies can also consider so-called arbitrage. In order to take advantage of these cost benefits, the storage facility needs to be emptied by midnight if possible so that it can then be refilled with cheap night-time electricity from the grid. The electricity could be put into operation in the morning, when the solar system is not yet producing at maximum capacity.

According to Röttger, this would only save 25 euros per day, but with an estimated 300 days a year, it would already save a total of 7,500 euros. Calculated over ten years, the payback period is then around ten months earlier.

Entegro Photovoltaik-Systeme GmbH has been on the market since 2009. Over the past 16 years, the solar industry in Germany has experienced highs - and above all - lows. According to Röttger, Entegro is one of the few companies to have successfully emerged from the trough. 45 employees recently generated 18.6 million euros in Germany and around the same amount in Turkey.

Incidentally, the second pillar in Turkey came about by a curious coincidence. The neighboring Fröndenberg kebab restaurant approached Entegro at some point with a question about solar systems. This gradually led to the construction of the solar power plant in the restaurant operator's home country.

Author: Volker Stephan