Let there be light - Professional terminology

The zero-energy house or even energy-gaining house is rather a vision than a currently realistic construction. The house is not supposed to consume additional energy for heating purposes. It is also supposed to transfer excess energy from solar systems to other consumers.   Heating demand of buildings in kilowatt hours per square meter and year:

Zero-energy house/Energy-gaining house: 0 KWh/m²*a, or excess energy.

Low-energy house: 40 - 79 KWh/m²*a.

Three-liter house: 16 - 39 KWh/m²*a.

Passive house: max. 15 KWh/m²*a.

Existent buildings, depending on heat insulation: 80 - 300 KWh/m²*a.