Even though most of the energy of the earth would not be present without the sun, only a few forms of power are considered to be solar power. In the context of renewable energy, solar power is associated with the harnessing of the sun's present emissions of heat or light.

Solar power, besides providing heat and light, also causes the wind that we feel here on Earth. Winds are created when various layers of the atmosphere absorb different amounts of heat and therefore expand differently. This creates regions of lower and higher pressure, resulting in masses of air that circulate both at ground level and at higher altitudes.

Solar power is also responsible for fossil fuels such as petroleum and coal. These substances are the result of large masses of decayed plant matter, which during their lifetime, absorbed solar energy. Fossil fuels are merely concentrated stores of the solar energy that these plants had while alive.

Power from the sun comes to the Earth as heat and light. This heat and light are the effect of the Sun's constant nuclear fusion of hydrogen nuclei. The process of fusion produces helium nuclei along with large amounts of energy. This energy is expressed as electromagnetic radiation (light is a specific frequency range of this radiation) as well as radiated temperatures of more than 6,100 degrees C. This is actually fairly cool compared with the corona and core of the sun that burn at several million degrees C. A small fraction of these extreme levels of energy that are released by the Sun come into contact with the Earth. The average amount of energy that contacts the Earth's surface in a day is 200 W/m2. [3] This means that the average home has more than enough roof space to produce enough electricity to supply all of its power needs. In fact, each day, more energy reaches the Earth from the sun than would be consumed by the global population in 27 years.

Solar power is renewable as long as the sun keeps burning the massive amount of hydrogen it has in its core. Even with the sun expending 700 billion tons of hydrogen every second, it is expected to keep burning for another 4.5 billion years. [5] Therefore, technically, solar power is not a completely renewable power source because it will be depleted in 4.5 billion years.

There are a variety of types of technologies associated with solar power. These technologies can be divided into two groups. The first group are those that use the sun to generate heat, called solar thermal technologies. Solar thermal technologies include solar concentrator power systems, flat plate solar collectors, and passive solar heating. [6] The other group of solar power technologies directly convert solar radiation into electricity through the photoelectric effect by using photovoltaics (also known as PV)

The amount to which a period of little or no sunlight will effect a home using solar power varies greatly depending on the physical location of a particular home and the nature of the solar system being used. For instance, if the home uses PV and solar thermal, and is also connected to the standard electricity grid, a period of no sunlight will simply mean relying on grid power. On the other hand, homes that are not connected to grid power must either be able to rely on other energy producers, such as a fuel cell, a wind turbine, a diesel generator, or on a supply of electricity stored in batteries. For some solar technologies, such as passive solar applications that utilize a large thermal mass, stored power in batteries or power from a standard utility cannot serve as a backup.

During operation, PV and solar thermal technologies produce no air pollution, little or no noise, and require no transportable fuels. One environmental worry with solar technologies is the lead-acid batteries that are used with some systems. This is a concern especially in developing countries where proper disposal and recycling is not always available. The impact of these lead batteries is lessening however as batteries become more recyclable, batteries of improved quality are produced and better quality solar systems that enhance battery lifetimes are created.

The second main method for capturing the sun's energy is through the use of photovoltaics. Photovoltaics (PV) utilize the sun's photons or light to create electricity. PV technologies rely on the photoelectric effect first described by French physicist Edmund Becquerel in 1839.

The photoelectric effect occurs when a beam of UV light, composed of photons (quantized packets of energy), strike one part of a pair of negatively charged metal plates. This causes electrons to be "liberated" from the negatively charged plate. These free electrons are then attracted to the other plate by electrostatic forces. This flowing of electrons is an electrical current. This electron flow can be gathered in the form of direct current (DC). This DC can then be inverted into alternating current (AC), which is the electrical power that is most commonly used in buildings.

Building integrated photovoltaics (BIPV) are photovoltaic materials that are used to replace conventional building materials in parts of the building envelope such as the roof, skylights, or facades. They are increasingly being incorporated into the construction of new buildings as a principal or ancillary source of electrical power, although existing buildings may be retrofitted with BIPV modules as well. The advantage of integrated photovoltaics over more common non-integrated systems is that the initial cost can be offset by reducing the amount spent on building materials and labor that would normally be used to construct the part of the building that the BIPV modules replace. In addition, since BIPV are an integral part of the design, they generally blend in better and are more aesthetically appealing than other solar options. These advantages make BIPV one of the fastest growing segments of the photovoltaic industry.

(Micro Combined Hear & Power)

Micro-CHP systems’ chief difference from their larger-scale kin is in the operating parameter-driven operation. In many cases industrial CHP systems primarily generate electricity and heat is a useful by-product. Contrarily, micro-CHP systems, which operate in homes or small commercial buildings, are driven by heat-demand, delivering electricity as the byproduct. Because of this operating model and because of the fluctuating electrical demand of the structures they would tend to operate-in, homes and small commercial buildings, micro-CHP systems will often generate more electricity than is instantly being demanded.

To date, micro-CHP systems achieve much of their savings, and thus attractiveness to consumers, through a "generate-and-resell" or net metering model wherein home-generated power exceeding the instantaneous in-home needs is sold back to the electrical utility. This system is efficient because the energy used is distributed and used instantaneously over the electrical grid.

These certificates can be sold and traded and the owner of the REC can claim to have purchased renewable energy. While traditional carbon emissions trading programs promote low-carbon technologies by increasing the cost of emitting carbon, RECs can incentivize carbon-neutral renewable energy by providing a production subsidy to electricity generated from renewable sources. 

Net metering is an electricity policy for consumers who own, generally small, renewable energy facilities, such as wind or solar power. "Net", in this context, is used in the sense of meaning "what remains after deductions" -- in this case, the deduction of any energy outflows from metered energy inflows. Under net metering, a system owner receives retail credit for at least a portion of the electricity they generate. The ideal has your existing electricity meter spinning backwards, effectively banking excess electricity production for future credit. In reality, the rules vary significantly by country and possibly state/province; if net metering is available, if and how long you can keep your banked credits, how much the credits are worth (retail/wholesale), etc.

Net Metering is generally a consumer-based renewable energy incentive. While it is important to have Net Metering available for any consumer that interconnects their renewable generator to the grid, this form of renewable incentive places the burdens of pioneering renewable energy primarily upon fragmented consumers. Often over-burdened energy agencies are not providing incentives on a consistent basis and it is difficult for individuals to negotiate with large institutions to recover their Net Metering credits and/or rebates for using renewable energy.

The carbon footprint is a measure of the exclusive global amount of carbon dioxide (CO2) and other greenhouse gases emitted by a human activity or accumulated over the full life cycle of a product or service (see Wiedmann and Minx, 2008).

Normally, a carbon footprint is expressed as a CO2 equivalent (usually in kilograms or tonnes), which accounts for the same global warming effects of different greenhouse gases (UK Parliamentary Office of Science and Technology POST, 2006). Carbon footprints can be calculated using a Life Cycle Assessment (LCA) method, or can be restricted to the immediately attributable emissions from energy use of fossil fuels. In both cases however, as the term usually indicates the amount of emissions generated through the actions of people, what is important is not only the total amount of energy use, but also how the energy was produced in the first place (e.g. from fossil fuels or renewable resources).