batteries Article Economics of Residential Photovoltaic Battery Systems in Germany: The Case of Tesla’s Powerwall Cong Nam Truong *, Maik Naumann, Ralph Ch. Karl, Marcus Müller, Andreas Jossen and Holger C. Hesse Institute for Electrical Energy Storage Technology, Technical University of Munich (TUM), Arcisstr. 21, 80333 Munich, Germany;
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[email protected]; Tel.: +49-89-289-26963; Fax: +49-89-289-26968 Academic Editor: Maciej Swierczynski Received: 8 February 2016; Accepted: 26 April 2016; Published: 11 May 2016 Abstract: Residential photovoltaic (PV) battery systems increase households’ electricity self-consumption using rooftop PV systems and thus reduce the electricity bill. High investment costs of battery systems, however, prevent positive financial returns for most present residential battery installations in Germany. Tesla Motors, Inc. (Palo Alto, CA, USA) announced a novel battery system—the Powerwall—for only about 25% of the current German average market price. According to Tesla’s CEO Elon Musk, Germany is one of the key markets for their product. He has, however, not given numbers to support his statement. In this paper, we analyze the economic benefit of the Powerwall for end-users with respect to various influencing parameters: electricity price, aging characteristics of the batteries, topology of battery system coupling, subsidy schemes, and retrofitting of existing PV systems. Simulations show that three key-factors strongly influence economics: the price gap between electricity price and remuneration rate, the battery system’s investment cost, and the usable battery capacity.