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. We reveal under which conditions a positive return on invest can be achieved and outline that the Powerwall could be a worthwhile investment in multiple, but not all, scenarios investigated. Resulting trends are generally transferrable to other home storage products.
Highlights
Residential battery energy storage systems (BESS) to increase the self-consumption of rooftop photovoltaic (PV) installations remain economically unfavorable for the German market under almost all conditions; considering battery prices of 2015, the savings of such systems under German market conditions commonly cannot surpass the battery investment cost within the estimated system lifetime as of [1,2].In spring 2015, Tesla Motors, Inc. (Palo Alto, CA, USA) announced the Powerwall, a BESS developed for residential PV-systems, surprising the renewable energy industry and gaining attention in the media
We present a comprehensive comparison of different parameters’ influence on the economics of residential BESS that increase the self-consumption of home-owners
The results show no distinct trend on the possible economic benefit regarding residential BESS in the price range of Tesla’s
Summary
Residential battery energy storage systems (BESS) to increase the self-consumption of rooftop photovoltaic (PV) installations remain economically unfavorable for the German market under almost all conditions; considering battery prices of 2015, the savings of such systems under German market conditions commonly cannot surpass the battery investment cost within the estimated system lifetime as of [1,2]. The technical specifications are similar to previous lithium-ion battery systems, but the announced system cost is significantly below the market prices of the time. The price of the Powerwall in Germany was announced to be about 500 EUR/kWh [4], reducing the specific price by a factor of four compared to previous average price for lithium-ion based systems. Multiple influencing factors—such as battery aging and variation of parameters—have not been considered in detail As such, these studies cannot be used to judge the system’s financial benefit for a given residential customer in Germany. The economic benefit of a system with technical data based on Tesla’s announcements regarding the Powerwall is assessed for the German market. This paper is organized as follows: Section 2 depicts the technical data of the analyzed BESS and the households; Section 3 describes the simulation model; Section 4 outlines the assumptions and scenarios investigated; Section 5 illustrates and discusses the simulation results; and Section 6 summarizes the findings and gives an outlook for future work
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