Sonnen GmbH

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sonnen GmbH
IndustryEnergy industry
Founded2010 (2010) in Wildpoldsried, Germany
FounderChristoph Ostermann and Torsten Stiefenhofer
Key people
  • Christoph Ostermann
  • Oliver Koch
  • Hermann Schweizer
  • Philipp Schröder[1]
RevenueIncrease €42 million[2][3] (2016)
OwnerRoyal Dutch Shell[4]
Number of employees
Increase 300[2] (2017)

sonnen GmbH (proprietary name and abbreviated form: sonnen) is a company in the energy industry headquartered in Wildpoldsried in the district of Oberallgäu, Germany. It produces home energy storage systems for private households and small businesses. The company is considered the market leader in Germany and additional international markets.[5] Moreover, it is the center of a community for supplying power from renewable energies.

Company development[edit]


Christoph Ostermann and Torsten Stiefenhofer founded the company in 2010 as a GmbH (German limited liability company). The legal name of the company at that time was PROSOL Invest Deutschland GmbH. In December 2013, the shareholders' meeting decided to change the company name to sonnenBatterie GmbH,[6] in order to adopt the name of its product range and to support the goal of internationalization.[7] Since November 2015, the company has operated as sonnen, under which all the company's individual activities are organized.[8]

Business development[edit]

From 2008 to 2010[9] above all founder Torsten Stiefenhofer developed a home battery marketed from 2011 under the name of sonnenBatterie. As a solar battery, the product is geared especially to independent homeowners with a photovoltaic system. As of mid-2016, eight generations of this power storage system have been developed and marketed.[10] Germany is the main sales market for the devices. The company also distributes the home batteries in Austria, Switzerland, United Kingdom, Ireland, Slovakia, Czech Republic, Italy, Netherlands, Sweden, Norway, the United States and Australia (current as of: October 2016).[11]

Along with the renaming of the company to Sonnen GmbH, the company announced in November 2015 that starting in 2016, it would establish its own power community, whose members can trade power among themselves.[12] Since September 2016, owners of a sonnenBatterie, who are a member of this power community, can obtain electricity at a flat rate.[13]

At the beginning of May 2017, TenneT and S sonnen announced their plans to implement decentralized photovoltaic domestic storage batteries using blockchain technology to help stabilize the power grid and improve the integration of renewable energies. This offers a new source of income to sonnen customers who take part in the system. Furthermore, the planned blockchain pilot project is meant to improve and simplify the networking of storage batteries, photovoltaic systems and power grids, as well as make them more efficient. From an economic perspective, this technology and sonnen’s battery pool (sonnenCommunity) could reduce the redispatching costs for stabilizing the power grid.[14][15][16]

Business fields[edit]

Power storage[edit]

Like other home storage systems, the sonnenBatterie from sonnen is also designed to increase the rate of own consumption of self-produced energy. Usually, a level of self-consumption of 30 to 55 percent can be reached with a photovoltaic system, when using smart-home functions. With a storage system, this rate is around 60 to 80 percent,[17] as the self-produced electricity can be stored until it is consumed within the household. There is less need to source external electricity, especially mornings or evenings.

Since its market launch, the company has designed the sonnenBatterie as a fully integrated system. In addition to the battery modules, it has an integrated power inverter, a unit for power management, along with electronic meters for power consumption in the building, for photovoltaic power generation and for feeding power into the grid or power-sharing in connection with the sonnenCommunity. The power management system evaluates the user's consumption data and takes weather statistics into account, in order to determine the optimal time intervals for charging and discharging the storage system. Moreover, the sonnenBatterie can be combined with heat pumps, small wind turbines or combined heat and power plants.[18][19]

The storage elements deployed are lithium iron phosphate batteries.[20] Sony is the main supplier of these components.[21] The various models of the system differ above all in their rated capacity, expressed in kilowatt hours. In Germany, Sonnen was one of the first suppliers of lithium ion batteries for stationary use in homes[22] and is considered market leader[23] in Germany and globally. Products are not distributed via wholesale trade but through selected specialty dealers.[24] From 2011 to mid-October 2016, 15,000 units were sold.[25] Most went to homeowners, along with farmers and small businesses.[26]


Since the first quarter of the year 2016, the company has organized the sonnenCommunity. It involves a power producer community of photovoltaic system operators (homeowners and small business owners), who share surplus power with one another.[12] In order to fill any power gaps in times when there is less sunlight, biogas systems are also included. Operators of small wind generators can also supply the community with power.[19][27]

The community combines three elements: the use of decentralized power generation, modern battery storage technology and digital networking of the participants. The concept is geared towards sonnen customers. The company grants prospective members a discount on the sonnenBatterie if they join the community. All members source power from the community at prices lower than from the grid. Moreover, sonnen handles the sale of surplus community power for them.[19][28]

By building up and expanding the community, the company hopes to boost sales of its sonnenBatterie. Besides, each community member pays a monthly fee to sonnen. The company in return handles the metering infrastructure and the software.[29]

The number of members at the beginning of October 2016 was around 3,000 households.[30] In May 2016, the company began building up the community in Austria.[31] The launch of the Swiss customer platform is announced for the 3rd quarter of 2016.[32]

Since September 2016, owners of a sonnenBatterie who are members of the sonnenCommunity can obtain electricity at a flat rate.[13][30][33]


In addition to the founders, several financial investors have equity stakes in the company (current as of: October 2016):

  • In January 2013, eCAPITAL entrepreneurial Partners AG,[34] acquired a 30 percent share in the company for EUR 3 million.[35]
  • The investment by Chrysalix SET Management B.V. (SET Ventures)[36] and Munich Venture Partners[37] was made at the end of 2014 as part of a capital increase of EUR 7.5 million, in which eCAPITAL also participated.[38]
  • In mid-2015, Inven Capital, investiční fond, a.s.,[39] a subsidiary of the Czech energy firm ČEZ, invested in the Allgäu-based company as part of an additional capital increase.[40] The investment involved a high single-digit sum in the millions.[41]
  • In June 2016, sonnen enlisted GE Ventures, the venture capital subsidiary of General Electric, as an additional investor.[42]
  • In October 2016, the company closed another funding round, resulting in EUR 76 million. All previous investors were involved. The Chinese corporate group Envision Energy[43] and Thomas Pütter, formerly CEO and ex-chairman of Allianz Capital Partners, were added as new investors.[44]
  • In February 2019, it was announced that Royal Dutch Shell would acquire 100% of the company for an undisclosed amount.[45]

Management and human resources[edit]

Up until the end of 2014, the founders managed the company.

At the beginning of 2015, there were changes in the management team. Hermann Schweizer replaced Torsten Stiefenhofer. The latter has since assumed the duties of Chief Innovation Officer. At the same time, the management team was supplemented by Oliver Koch, who had previously converted individual production of the battery systems over to series production.[46]

Starting in October 2015, Philipp Schröder[47] switched from Tesla Motors back to the then sonnenBatterie GmbH and is responsible as a member of management for Sales and Marketing.[48] Within a few months, six additional Tesla managers followed him.[49]

Since the company's founding up to the summer of 2016, the number of employees has increased 20-fold. In June 2016 it was roughly 200, of whom 140 were employed in Wildpoldsried.[21] In September 2016, the number of employees was 250 in total.[50][30] At the beginning of 2017, some 300 employees worked for the company.[2]


Up to the end of 2015, the company manufactured its battery storage systems exclusively in Wildpoldsried. Here production occurred for marketing under the company's own name and also as a white-label manufacturer for companies such as SolarWorld and RWE.[51] In 2015, the company established a production facility in San Jose, California.[52] Here the company has been producing for the US market since the end of 2015.[53] In June 2015, the company set up a location in Atlanta (Georgia) for research and development, in order to adapt its own products to the conditions in the United States market.[54]


The company has received several prizes and awards:

  • In 2017, it received the Zayed Future Energy Prize in the category Small and medium-sized enterprises.[55]
  • The Massachusetts Institute of Technology (MIT) honored the company in 2016 as one of the 50 Smartest Companies 2016 worldwide.[56][27]
  • Out of 6,900 candidates, the company was inducted into the Global Cleantech 100 list for the year 2015 at the Cleantech Forum in San Francisco. The panel of judges consider it one of the most innovative companies in the category of Europe & Israel.[57]
  • sonnen GmbH was among the winners in the comparison of home batteries carried out by the market and social research firm EuPD Research and the results of which were published by Wirtschaftswoche in June 2016.[58]
  • The company is among the winners of the StartGreen Award 2015.[59]
  • In October 2015, the company was dubbed Wachstumschampion by Focus magazine. According to a statement by Focus and Statista, the company was among the ten fastest-growing enterprises in Germany.[60]
  • In 2014, the company received the EUR 100,000 Step-Award from FAZ-Institut and the industrial park operator Intraserv GmbH & Co. Höchst KG.[61]


The company is a member of the Arbeitsgruppe Energiespeicher of the Bundesverband Solarwirtschaft and member of the Bundesverband Energiespeicher (BVES).[62]

External links[edit]


  1. ^ Legal notice of the website of sonnen, retrieved October 11, 2016.
  2. ^ a b c "Solar-Firma Sonnen plant Börsengang". (in German). January 1, 2017. Retrieved April 4, 2017. Cite has empty unknown parameters: |day= and |month= (help)
  3. ^ Andreas Knoch (March 13, 2017). "Allgäuer Start-up greift Energiekonzerne an". Schwäbische Zeitung (in German). Retrieved April 4, 2017. Cite has empty unknown parameters: |day= and |month= (help)
  4. ^ "sonnen appoints new UK lead as it targets storage, VPP growth". Solar Power Portal. Retrieved January 29, 2020.
  5. ^ Sandra Enkhardt (October 27, 2016). "EuPD Research: sonnen und Senec führend auf deutschen Photovoltaik-Speichermarkt". Retrieved November 1, 2016. "Energiespeicher: Deutsche Anbieter führen bei Marktanteilen". October 27, 2016. Archived from the original on November 1, 2016. Retrieved November 1, 2016. "sonnen (not Tesla) is the global leader in solar linked energy storage". October 27, 2016. Retrieved November 1, 2016.
  6. ^ Bundesanzeiger, Commercial Register announcements on PROSOL Invest Deutschland GmbH, January 15, 2014, date of entry January 8, 2014.
  7. ^ Statement by Christoph Ostermann in an interview with Mirco Sieg. See "Prosol Invest/sonnenbatterie: Erfolgreich trotz Speicherförderung". December 19, 2013. Retrieved September 22, 2016.
  8. ^ Statement by Christoph Ostermann in an Interview with Engelbert Hopf. See sonnenCommunity: Der mögliche Anfang vom Ende herkömmlicher Stromversorger. Ein Startup auf dem Weg zum 100-Mio.-Euro-Unternehmen. In: Markt&Technik, 27/2016.
  9. ^ See Daniel Pohl: Lithium iron phosphate: With the genes of a marathon runner. In: ees International. The Electrical Energy Storage Magazine, 1/2014, p. 33–37, here p. 36. Benjamin Reuter: Energie: Diese Heimbatterie soll den Strommarkt aufmischen. In: WirtschaftsWoche Green, June 5, 2014. Benjamin Reuter: Cleantech-Startups: Das sind die Champions aus Deutschland. In: WirtschaftsWoche Green, October 15, 2014.
  10. ^ Angela Kanders (June 15, 2016). "Batteriespeicher liegen im Wachstumstrend – Wirtschaftsinstitute erwarten für dieses Jahr Neuinstallationen von rund 20.000 Stromspeichern". Retrieved September 22, 2016.
  11. ^ Henrik Petersen: Speicher sind keine Verbraucher. In: Photovoltaik, 4/2015, p. 66–71, here p. 70. Cosmin Laslau (January 29, 2015). "E.ON's new focus on renewables and what it could mean for energy storage and distributed generation". Retrieved September 22, 2016. Sandra Enkhardt (May 11, 2016). "sonnen setzt im 1. Quartal mehr sonnenBatterien ab als Tesla Powerwalls". Retrieved September 22, 2016. sonnenBatterie mit neuen Rekorden. In: Allgäuer Zeitung, May 21, 2016. "Solar Electric Ireland wins 'Product of the Show' at Energy Awards". July 2, 2016. Retrieved October 6, 2016. Jan Brož (July 21, 2016). "ČEZ připojil první soláry na baterii z Německa. Investice se vrátí za 13 let". Retrieved October 6, 2016. sonnenBatterie ab sofort auch in Norwegen verfügbar. Press release of the company of October 11, 2016. See also the Website of the Swedish company CRenergy, retrieved October 6, 2016 and the Website of sonnen, retrieved October 5, 2016.
  12. ^ a b Nils-Victor Sorge (November 26, 2015). "Wie sieben Ex-Tesla-Manager RWE und Eon abschaffen wollen". Manager Magazin. Retrieved September 22, 2016. Andreas Menn: Brüder, zur Sonne, zur Freiheit. In: WirtschaftsWoche, November 27, 2015.
  13. ^ a b Wolfgang Kempkens (September 12, 2016). "Tschüss, Stromrechnung. Unternehmen bringt Solar-Flatrate auf den Markt". WirtschaftsWoche. Retrieved September 22, 2016.
  14. ^ Bauchmüller, Michael (May 1, 2017). "Rettungsnetz für den Strom". Süddeutsche Zeitung. Retrieved June 6, 2017.
  15. ^ Sandra, Enkhardt (May 2, 2017). "sonnen und Tennet vernetzen Photovoltaik-Heimspeicher per Blockchain-Technologie". Retrieved June 6, 2017.
  16. ^ Daniel Wetzel (May 2, 2017). "Die Tür in eine völlig neue Energiewelt". Die Welt (online) (in German). Retrieved June 6, 2017. Cite has empty unknown parameters: |day= and |month= (help)
  17. ^ sonnen strom auch nachts? In: Öko-Test Ratgeber Bauen und Wohnen 2015, p. 100–105, here p. 101. „Mit Speichern unabhängiger werden“. In: EffizienzHäuser, 6/7-2015, p. 48 f, here p. 48. ""Intelligente sonnenBatterie" unter den Top 50". September 22, 2016. Retrieved October 5, 2016. Walther Rosenberger (September 20, 2016). "Nie wieder eine Stromrechnung". Stuttgarter Nachrichten (online). Retrieved October 10, 2016.
  18. ^ See also the technical specifications of the manufacturer on their website. For integrated use of sonnenBatterie, photovoltaic systems and combined heat and energy plants, sonnen works with Vaillant among others, see Wolfgang Kempkens (July 21, 2014). "So koppeln sich Hausbesitzer von der Stromversorgung ab". WirtschaftsWoche Green. Retrieved September 22, 2016.
  19. ^ a b c Heiko Schwarzburger: Endkunden virtuell vernetzt. In: Photovoltaik, 12/2015, p. 72–74, here p. 73.
  20. ^ See Reinhard Siekemeier, Ralf Ossenbrink: Solare Energie auf Vorrat. In: Sonne Wind & Wärme, 13/2011, p. 170–174, here p. 174. Uwe Bonnen: Funktioniert auch nachts und bei schlechtem Wetter. Neue Rezepte gegen steigende Nebenkosten. In: ew. Magazin für die Energiewirtschaft, 110 (2011), 26–27, p. 68 f. here p. 69. Michael Kerler: Öko-Strom aus dem Schrank. In: Augsburger Allgemeine, September 29, 2012.
  21. ^ a b Auf dem Weg zur dezentralen Energieversorgung. In: Straubinger Tagblatt/Landshuter Zeitung, June 21, 2016.
  22. ^ Jochen Knoblach (May 15, 2015). "E-Mobil-Hersteller Tesla Tesla treibt mit Hausbatterien die Energiewende voran". Berliner Zeitung (online). Retrieved September 22, 2016. The article erroneously states that Sonnen was the first supplier.
  23. ^ Energy storage demand ramps up in Germany's residential PV market. In: Energy Storage Journal, Spring 2016, S. 37–40, here p. 39. "sonnen (not Tesla) is the global leader in solar linked energy storage". October 27, 2016. Retrieved November 1, 2016. Sandra Enkhardt (October 27, 2016). "EuPD Research: sonnen und Senec führend auf deutschen Photovoltaik-Speichermarkt". Retrieved November 1, 2016. "Energiespeicher: Deutsche Anbieter führen bei Marktanteilen". October 27, 2016. Archived from the original on November 1, 2016. Retrieved November 1, 2016.
  24. ^ Ina Röpcke: Mit Leidenschaft verkaufen. In: Sonne Wind & Wärme, 10/2013, p. 94–97, here p. 95., ed. (March 21, 2016). "sonnen hat keine Angst vor Tesla Powerwall". Retrieved September 22, 2016.
  25. ^ Vera Eckert (October 16, 2016). "China's Envision joins investors in German battery firm sonnen cash boost". Retrieved October 17, 2016.
  26. ^ Illustration of use in agriculture: Eine Batterie für den sonnen-Strom. In: Allgäuer Zeitung, May 22, 2014. And: Eigenstrom effektiver nutzen. In: Bayerisches Landwirtschaftliches Wochenblatt, June 27, 2014. Illustration of an application in the commercial sector: sonnenBatterie: Strom auf Vorrat. In: Hotel & Technik. Das Magazin für Hoteliers, Planer und Investoren, 6/2013, p. 54 f.
  27. ^ a b Inge Kloepfer (December 6, 2016). "Strom aus dem Schrank". (in German). Retrieved April 4, 2017. Cite has empty unknown parameters: |day= and |month= (help)
  28. ^ Schwarmspeicher für die Community. In: ZfK Zeitung für kommunale Wirtschaft, January 11, 2016. See also Felix Austen: Das Stromdepot im Keller. In: Bild der Wissenschaft April 27, 2016. Beate Oberkofler (May 18, 2016). "Solarstromspeicher im Haus werden wirtschaftlich. Neue Konzepte unterstützen die Energiewende". press release, Retrieved October 22, 2016. The sonnenCommunity. Energy freedom and energy community. In: pv magazine 6/2016.
  29. ^ Beate Oberkofler (May 18, 2016). "Solarstromspeicher im Haus werden wirtschaftlich. Neue Konzepte unterstützen die Energiewende". press release, Retrieved September 22, 2016.
  30. ^ a b c Helmut Bünder (October 7, 2016). "Strom von Nachbarn oder lieber vom E-Mail-Provider?". (Frankfurter Allgemeine Zeitung). Retrieved October 10, 2016.
  31. ^ "Sonnen startet Kundenplattform in Österreich". energate messenger. May 2, 2016. Retrieved September 9, 2016.
  32. ^ Swisscom Energy Solutions setzt auf Sonnencommunity. energate Messenger Schweiz, June 20, 2016.
  33. ^ Caroline Strang (October 8, 2016). "Sonnen GmbH: Eine Flatrate für Strom". Alp Bote. Retrieved October 10, 2016.
  34. ^ Website of eCAPITAL.
  35. ^ Benjamin Heimlich: „Jetzt ist die Zeit zu investieren“. In: VentureCapital Magazin. Special supplement Cleantech, 2013. p. 10 f. Andrea Martens: Wo weniger mehr ist. In: Unternehmeredition Private Equity / M&A, 2014, p. 6–14, here p. 14.
  36. ^ Website of SET Ventures.
  37. ^ Website of Munich Venture Partners.
  38. ^ Marc Roca (December 3, 2014). "sonnenBatterie beendet Finanzierungsrunde, neue Märkte im Visier". (Bloomberg News-Meldung). Retrieved September 9, 2016. Stefan Paravicini: Start-ups haben die Energiewende schon lange eingeläutet. In: Börsen-Zeitung, December 3, 2014.
  39. ^ Website of Inven Capital, investiční fond, a.s.
  40. ^ Jason Hovet (July 9, 2015). "Czech CEZ unit takes minority stake in German firm sonnenBatterie". Reuters. Retrieved September 22, 2016.
  41. ^ sonnenBatterie erhält Geld von Investor. In: Allgäuer Zeitung, July 11, 2015
  42. ^ Nils-Victor Sorge (June 6, 2016). "General Electric verbündet sich mit bayerischem Mittelständler gegen Tesla". Manager Magazin (online). Retrieved September 22, 2016. "GE steigt bei Allgäuer aonnen GmbH ein". Handelsblatt (online). June 6, 2016. Retrieved September 22, 2016. Vera Eckert, Andreas Cremer, Alexandra Hudson (June 6, 2016). "German battery maker sonnen GmbH wins backing from GE". Reuters. Retrieved September 22, 2016.CS1 maint: multiple names: authors list (link) Patrick McGee (June 6, 2016). "GE takes stake in German renewable battery group sonnen". Financial Times. Retrieved September 22, 2016.
  43. ^ Website of Envision Energy.
  44. ^ Brian Parkin (October 16, 2016). "sonnen Considering IPO in Bid to Rival Tesla Powerwall Storage". Retrieved October 17, 2016. Vera Eckert (October 16, 2016). "China's Envision joins investors in German battery firm sonnen cash boost". Retrieved October 17, 2016. "Duitse fabrikant van zonne-energieaccu's sonnen overweegt beursgang (Dutch)". Het Financieele Dagblad. October 16, 2016. Retrieved October 17, 2016. Brian Parkin (October 17, 2016). "sonnen GmbH erwägt Börsengang womöglich schon im kommenden Jahr". Die Welt (online). Retrieved October 18, 2016. sonnen sammelt 76 Millionen ein. In: Handelsblatt, October 17, 2016.
  45. ^ "Shell buys German solar battery maker sonnen". Reuters. February 15, 2019. Retrieved April 30, 2019.
  46. ^ Sandra Enkhardt (January 23, 2015). "sonnenBatterie verzeichnet anhaltend hohe Nachfrage". Retrieved September 22, 2016. Manfred Gorgus (February 3, 2015). "Personalkarussel bei der sonnenBatterie GmbH". Retrieved September 22, 2016. See also the entry on Oliver Koch in Bundesanzeiger, January 22, 2015.
  47. ^ Porträt: Ruth Fend, Kerstin Zilm: Gegen den Stromriesen. In: Business Punk, 4/2016, August 4, 2016, p. 64–72.
  48. ^ Nils-Victor Sorge (August 19, 2015). "Teslas Deutschland-Statthalter geht nach 20 Monaten". Manager Magazin (online). Retrieved September 22, 2016. Elektropionier Tesla verliert seinen Deutschland-Chef. In: Frankfurter Allgemeine Zeitung, August 26, 2015.
  49. ^ Rebecca Eisert (November 9, 2015). "Managerschwund bei Tesla Deutschland". WirtschaftsWoche. Retrieved September 22, 2016.
  50. ^ ""Intelligente sonnenBatterie" unter den Top 50". September 22, 2016. Retrieved October 5, 2016.
  51. ^ For information on this cooperation, see "Batteriespeicher: RWE Tochtergesellschaft entdeckt Solar". December 9, 2013. Retrieved September 23, 2016. Karsten Wiedemann (April 26, 2013). "Solarspeicher-Markt vor deutlichem Wachstum". Retrieved September 23, 2016. Also: Energy storage demand ramps up in Germany's residential PV market. In: Energy Storage Journal, Spring 2016, p. 37–40, here S. 39., ed. (March 21, 2016). "sonnen hat keine Angst vor Tesla Powerwall". Retrieved September 22, 2016.
  52. ^ Ivan Penn (October 11, 2015). "New ways to put energy in the bank". Los Angeles Times. Retrieved September 23, 2016.
  53. ^ Sandra Enkhardt (December 17, 2015). "sonnenBatterie vor Tesla-Powerwall. Erste Photovoltaik-Speichersysteme an Privathaushalte ausgeliefert". Retrieved September 23, 2016.
  54. ^ Phil W. Hudson (June 10, 2015). "German company opens Atlanta R&D facility to battle Tesla". Atlanta Business Chronicle (per Retrieved September 23, 2016.
  55. ^ Sandra Enkhardt (January 16, 2017). "sonnen erhält Zayed Future Energy Prize". (in German). Retrieved April 4, 2017. Cite has empty unknown parameters: |day= and |month= (help)
  56. ^ List of award winners 2016, retrieved September 23, 2016.
  57. ^ List of those honored in the year 2015. Sandra Enkhardt (January 28, 2016). "sonnenbatterie als innovativstes Unternehmen Europas 2015 ausgezeichnet". Retrieved September 23, 2016. Bürger setzen Energiewende vor Ort um. In: Bayerische Staatszeitung, February 26, 2016.
  58. ^ Peter Vollmer: Daimler schlägt Tesla, in: Wirtschaftswoche, Nr. 25, June 17, 2016. See also Peter Vollmer (June 20, 2016). "Das sind die 93 besten Stromspeicher für Zuhause". Wirtschaftswoche (online). Retrieved October 5, 2016.
  59. ^ Information on the award and on the 2015 laureates, retrieved September 23, 2016.
  60. ^ See Focus Spezial: Wachstumschampions 2016. See also Wachstumspreis für die sonnenBatterie. In: Allgäuer Zeitung, November 28, 2015 and Bürger setzen Energiewende vor Ort um. In: Bayerische Staatszeitung, February 26, 2016.
  61. ^ 100000-Euro-Preis für die sonnenBatterie GmbH. In: Allgäuer Zeitung, January 10, 2015.
  62. ^ "Die Solarbatterien der PROSOL Invest Deutschland GmbH – sonnenBatterie GmbH". January 5, 2014. Retrieved September 23, 2016.