The primary energy requirement takes into account, alongside the energy requirement for heating and hot water also the losses, which the energy suppliers incur in production, whose preparation and transport also the energy loss from the heating equipment. Bio-Solar-Houses require neither oil, gas, nor electric for heating. They use almost exclusively renewable energy sources such as sun and wood for heating and hot water.

Since solar energy does not cost much to produce, wood is a locally available and renewable fuel and the heating equipment has virtually no energy loss, Bio-Solar-Houses have an extremely low primary energy requirement. When comparing the energy consumption of houses it does not therefore depend on their low heating energy requirements, but rather on their low primary energy requirements.
This is at one and the same time a measure for their energy efficiency and their environmental protection.

Efficiency is the measure for sustainable economic actions.
Efficiency is the correct thing to do correctly.