The Gemini house is a prototype design for a house that uses solar energy and efficient design.

Roland Mosl created the concept in autumn 1991. The name expresses a design goal: The real estate used should serve two purposes simultaneously -- living and generating solar electricity. In 1993 Roland Mosl wrote a book about the project in German language: Aufstieg zum Solarzeitalter (Advance to the solar age). The project won a prize at the 1993 EUREKA world innovation fair in Brussels. In 2001 there was a national exhibition about energy in Styria, Austria. As main attraction of that exhibition, a prototype was built in Weiz, a small town north of Graz in Austria. Constructed to generate more electricity than its inhabitants consume, it was the first energy plus house in Austria.

The house is cylindric and rotates to follow the sun. It is equipped with up to 150m2 of photovoltaic panels. Extreme thermal insulation and heat recovery from waste air are also included.