Passive solar energy to put simply uses sunlight for energy without mechanical systems. It consists of a home or structure that is configured and designed to naturally harness the power of the sun in the form of heat. The passive energy technologies convert sunlight into usable heat for water, air or thermal mass; they cause air movement used for ventilation, or store heat for future use without assistance of other energy sources. A good example of passive energy is a solarium located on the equator side of the building. Passive solar power is also used to describe the technology used to reduce summer cooling requirements, known as passive cooling. With some passive solar power use a small amount of conventions energy to control things like dampers, shutters, night insulation or other items that enhance passive energy, whether it is for storage, energy collection, use or unnecessary heat transfer.

The technologies used to collect passive energy include direct and indirect solar gain for space heating, water heating systems based on thermosiphon, which is a method of passive heat exchange based on natural convection, which circulates liquid in a vertical loop without requiring a conventional pump. Passive energy that has low grade energy needs, like space or water heating, tend to be better applications for passive solar energy utilization.

Some examples of passive energy are solar tubes and skylight as well as good insulated windows which all provide good lighting especially in a bathroom to allow natural light to provide the room with lighting and therefore saving on electricity. It once was popular to use passive solar energy to heat water to run steam engines, this may be a form of energy many turn back to due to the expensive nature of fossil fuels. In some regions gardeners have connected greenhouses to their houses then the sun and plants heat the homes at no extra cost.

When it comes to building a passive solar home or structure the placement on the property is the key factor in building a successful and energy efficient structure. The most important factor to consider when building a passive energy solar home is the shadows, positioning the most windows to receive the most sun possible; this will maximize solar radiation penetration to the home and therefore the amount of heat that can be captured. Remember to take into consideration the position of the sun during the different seasons, shade in the summer months and sun in the winter months.

There are many benefits to passive solar energy systems once set up they have little or no operating costs, very little or low maintenance costs. These solar energy systems are very earth friendly and emit no greenhouse gasses.