Solar energy does not only generate electricity but it also can be used for passive heating. Using solar energy for passive heating is a very economical solution because it minimizes energy use. A passive solar building uses the movement of the sun throughout the day (considering seasonal changes in sunlight) to heat houses. The most important factors in passive solar design are windows by which the sunlight can pass through, absorbers which keep the warmth and the distribution of heat circulation. There are different requirements for different locations. For example in the northern hemisphere windows should be oriented south, while in the southern hemisphere windows oriented north are ideal. The disadvantage of a passive building is that if a house was not originally built in this technology, the renovation cost would be expensive. Even then, there is still the possibility to take steps that minimize the wasting of passive solar energy and minimize your long-term costs. It is possible to use a solar heating system such as solar collectors, which can be used for hot water or even as a source of house heating. The other option for using solar energy is electricity generated with photovoltaic (PV) panels, which can be used together with solar collector systems.