Economics of Residential Photovoltaic Battery Systems in Germany: The Case of Tesla’s Powerwall

TLDR

Residential PV battery systems boost self‑consumption and lower bills, yet high costs usually preclude positive returns; Tesla’s Powerwall, priced at roughly 25 % of the German average, is marketed as a cost‑effective alternative, though specific financial data are lacking. This study evaluates the economic benefit of the Powerwall for end‑users across parameters such as electricity price, battery aging, system topology, subsidies, and PV retrofitting. We analyze the Powerwall’s economics by simulating scenarios that vary electricity price, remuneration rate, battery cost, usable capacity, aging, coupling topology, subsidies, and PV retrofitting. Simulations reveal that the price gap between electricity and remuneration, the investment cost, and usable capacity are the key drivers of profitability, indicating that the Powerwall can yield positive returns in some but not all scenarios, a trend transferable to other home storage products.

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.