The “AktivPLUS” multi‑family house in Stuttgart‑Möhringen was built to demonstrate a nearly climate‑neutral residential standard that meets the EU “nearly‑zero‑energy‑building” requirement. The 22‑unit dwelling, completed in early 2021, combines high‑performance construction, a large thermal buffer, and a sophisticated renewable‑energy system. Its location next to the Stuttgart‑Möhringen train station demanded stringent acoustic protection, which was achieved through the building’s design and construction.

Heating and domestic hot water are supplied by a single water‑to‑water heat pump that draws heat from a dedicated mixed‑water channel. The system is coupled to a 6,500‑liter buffer tank that smooths the heat‑pump cycling and allows the photovoltaic (PV) array to operate at higher self‑consumption rates. Heat is delivered through low‑temperature underfloor heating (maximum supply temperature 40 °C) and decentralized drinking‑water stations that reduce the required hot‑water supply temperature, thereby improving overall system efficiency. The heat‑pump’s electrical consumption is the largest share of the building’s electricity use, but the large buffer and low‑temperature distribution keep the system highly efficient.

The building’s renewable‑energy portfolio consists of a 78 kWp rooftop PV system and a 4 kWp organic PV array on the balcony railings. A 227 kWh nickel‑manganese‑cobalt battery stores excess solar generation and is managed by an overarching load‑management scheme that prioritises self‑consumption. Over the two‑year monitoring period (July 2021–July 2023) the building consumed 196.5 MWh of electricity, averaging 66 kWh per square metre per year. Solar self‑consumption ranged from 68 % to 76 % depending on the optimisation target, while the combined solar‑plus‑battery contribution reached about 50 %. The battery operated with an efficiency of roughly 70 %, effectively reducing grid imports during night hours. Heating consumption largely matched the design targets, but overall electricity use exceeded the planned values, partly due to increased occupancy during COVID‑19 lockdowns. The EnergyPLUS balance remained slightly negative throughout the observation period, indicating that the building did not fully achieve the target climate‑neutral standard, although it came close.

Carbon‑footprint analysis shows that the building draws about 10 t of CO₂‑equivalent electricity from the grid per year and exports roughly 5 t back to the grid, resulting in an annual emission of 9–12 kg CO₂ per square metre of living area. These figures demonstrate the potential of the integrated system to reduce the building’s net emissions, even though the target of a fully climate‑neutral operation was not met.

The project was carried out by a consortium of partners. The Steinbeis Transferzentrum for Energy, Building and Solar Technology led the scientific monitoring and optimisation programme. Bietigheimer Wohnbau GmbH acted as the developer and owner. EGS‑plan Ingenieurgesellschaft für Energie‑, Gebäude‑ und Solartechnik mbH provided the energy concept, building physics, and heating‑load‑supply planning. enisyst GmbH supplied measurement, control, and regulation technology, while Stadtwerke Stuttgart GmbH operated the building’s utilities. The architects were represented by the Freie Architekten and the Böhme Hilse Diplomingenieure. The project was funded under the German federal National Action Plan Energy (NAPE) and ran for two years of operation and monitoring, delivering valuable insights into the feasibility of near‑zero‑energy multi‑family housing.