Worldwide, solar energy is considered as one of the most promising sources of green energy around the houses. It is a prime source of renewable energy due to its constant availability (except at night, and even then, it can be stored in batteries) and ease of use (photovoltaic cells are solid-state, with no moving parts).

Solar energy increased 83% in number of installations worldwide in 2009. Once found only in water-heating systems and in less-energy-hungry devices such as watches and calculators, solar power has now found its way into vehicles such as cars, buses and even airplanes, and can now be configured to suit almost any household electrical need.

Solar energy is widely understood as any form of energy that comes from the sun. In the power-generation industry, solar energy is divided into two major kinds: photovoltaic cells and CSP or concentrating solar thermal powerPhotovoltaic cells convert solar radiation into electricity through the use of semiconductors, while CSPs use lenses and mirrors to focus sunlight onto water pipes, generating electricity via the conventional steam turbine.

A third category combines the preceding two, and is known as concentrated photovoltaics (CPV). Of the three, the photovoltaic technology (PV) is deemed most practical in producing small-scale green energy around the houses of people.

Currently, building-integrated photovoltaics (BIPVs) are favored additions to newer infrastructures, either as principal or auxiliary sources of electric power. Most of these devices produce from 1 to 10 kilowatts (at $1.80 per watt in 2010, and expected to decline to about $1.50 per watt by the end of 2011).

A significant obstacle in the use of BIPVs is the capital installation cost, which is speedily decreasing. Overall, domestic applications of solar power generation are replacing some of the other existing sources, especially in the developing world, bringing green energy around the houses of those who have them.