Wilhelmshavener Spar- und Baugesellschaft eG is a pioneer in the construction of Germany's first energy-autonomous apartment building. For the first time, an apartment building enables its residents to obtain two thirds of their heat and electricity from their own resources. This means enjoying an energy flat-rate for the tenants. For SPAR+BAU, it means a model project.

SPAR+BAU created six apartments of about 90 square metres each. They are more than just comfortably equipped residential space with two free e-charging places in front of the building. The builder used innovative building technology with a clear goal: solar and ecological local energy supply for a building of high quality in energy and structural respects. Solar and photovoltaic modules on the roof, the balcony cladding and the south façade cover around 31,700 kilowatt hours of the tenants' annual energy requirements from solar energy. This permits a flat-rate rent that includes the housing fee as well as the costs for heat, water, electricity and even e-mobility.

For the tenants in Bismarckstraße, this means: Energy at a flat rate, with transparency and cost security. Displays in the living rooms inform them about their current and past consumption every day. The monthly flat-rate rent of 10.50 Euro/m² includes an annual consumption limit of 3,000 kilowatt hours per residential unit for electricity and heating, and 100 cubic metres per year for water. This corresponds to the average consumption in conventional buildings, with a safety margin added on. Tenants and landlords alike also spare themselves the annoying matter of settling utility costs. For comparison: While the comparable base rent in a new building in Wilhelmshaven is around 8.25 Euro/m², residents here only pay 6.95 Euro/m². In addition to cost security, this gives them an advantage of around 120 Euro per month as compared to the conventional base rent.

An approximately nine-metre-high, long-term heat storage tank with a volume of 20,000-litre is a core element of the thoroughly insulated building. It is connected to the public grid and can be "tapped" by the tenants at need. The generated power is stored in two 22 kWh batteries. Solar thermal energy and photovoltaics, together with thermal and electrical long-term storage, produces and stores energy to be consumed later in the energy-autonomous building. The building has a degree of self-sufficiency of around 70 percent. The remaining heat demand in winter is covered from a natural-gas heater. Electricity is drawn from the public grid as required during that season. Any electricity and heat surplus generated goes to two e-charging stations outside the building and also supplies adjacent apartment buildings from spring to autumn.