Purpose: The purpose of this degree project was to compare the differences in energy demand for three different sizes of smaller, detached one-family houses in Sweden, and to investigate the advantages and challenges of living in a significantly smaller house than the typical Swedish one-family house. Method: The comparison was made between one typical sized detached one-family house and two significantly smaller houses of the same technical standard. The differences in energy demand for the three houses focused on heat losses, passive heat gain and the demand for active heating. To investigate the advantages and challenges of living in significantly small houses information was gathered through different sources of literature and from other people’s experiences. Results: The result showed that the smallest of the three houses had 87 percent lower demand for active heating than the largest house, and the second smallest house had 59 percent lower demand for active heating than the largest house. In addition, the heating season for the smallest houses was three months shorter per year than for the other two houses. The advantages of living in a significantly smaller house than the typical Swedish one-family house was mainly economically and environmentally based. The challenges were mainly the limited space that a smaller living area entails. Conclusions: The project concluded that there is a significant amount of energy that can be saved by choosing to live in a smaller house than the typical Swedish one-family house, and that the advantages of living in a smaller house was greater than the challenges.