Solar energy is one of the most abundant and freely available sources of energy on our planet. The amount of solar energy that hits planet’s surface in a day is bigger than the planet’s yearly total energy demand. Although it sounds like the perfect renewable source of energy, the amount of solar energy that we can use varies depending on the time of day, season as well as geolocation. Solar energy is popular as an energy source that supplements our energy consumption.

Wind is also an abundant source of green energy. Turbines are used in order to harness this energy and transfer it to generators that later feed the produced electrical energy in the national network. Although there are local and off-grid systems, not every property is suitable for a local wind turbine.

Hydropower is one of the most commercially developed renewable sources of energy. By building a dam or an obstacle of sorts, the big reservoir of water can be used to create a controlled stream of water to the turbine, which will later generate electric energy. This can be more reliable than solar or wind power (specially if its tidal and not riverine) and can also allow for the electrical energy to be stored for further use in peak demand periods. As well as wind power, hydro power can be a more cost-effective commercial energy source (depending on the type and compared to other energy sources), but depending on the type of the property it can be used for domestic, out-of-grid solution.

Geothermal energy can be used as a domestic heating source by using the natural heat in the soil. It can also be used to create electric energy. In many countries the geothermal energy is insufficiently used although it is a very cost-effective source of energy that is good for the environment and the soil. There are also positive examples of geothermal energy usage, such as the Island example, where it is considered to be one of the most important heat energy sources.