A photovoltaic system for residential, commercial, or industrial energy supply consists of the solar array and a number of components often summarized as the (BOS). This term is synonymous with "" q.v. BOS-components include power-conditioning equipment and structures for mounting, typically one or more DC to power converters, also known as , an energy storage device, a racking system that su. A photovoltaic system for residential, commercial, or industrial energy supply consists of the solar array and a number of components often summarized as the (BOS). This term is synonymous with "" q.v. BOS-components include power-conditioning equipment and structures for mounting, typically one or more DC to power converters, also known as, an energy storage device, a racking system that supports the solar array, electrical wiring and interconnections, and mounting for other components. Optionally, a balance of system may include any or all of the following: revenue-grade meter, (MPPT), system and, ,, sensors,, or task-specific accessories designed to meet specialized requirements for a system owner. In addition, a system requires or mirrors and sometimes a cooling system. The terms "solar array" and "PV system" are often incorrectly. A photovoltaic system, also called a PV system or solar power system, is an designed to supply usable by means of . It consists of an arrangement of several components, including to absorb and convert sunlight into electricity, a to convert the output from to, as well as,, and other electrical accessories to set up a working system. Many utility-scale PV systems use that follow the sun's daily path across the sky to generate more electricity than fixed-mounted systems. Photovoltaic systems convert light directly into electricity and are not to be confused with other solar technologies, such as or, used for heating and cooling. A solar array only encompasses the solar panels, the visible part of the PV system, and does not include all the other hardware, often summarized as the (BOS). PV systems range from small, or systems with capacities ranging from a few to several tens of kilowatts to large, of hundreds of megawatts. Nowadays, off-grid or account for a small portion of the market. Operating silently and without any moving parts or, PV systems have evolved from niche market applications into a mature technology used for mainstream electricity generation. Due to the, prices for PV systems have rapidly declined since their introduction; however, they vary by market and the size of the system. Nowadays, solar PV modules account for less than half of the system's overall cost, leaving the rest to the remaining BOS components and to soft costs, which include customer acquisition, permitting, inspection and interconnection, installation labor, and financing costs. A system converts the Sun's, in the form of light, into usable . It comprises the solar array and the balance of system components. PV systems can be categorized by various aspects, such as, vs. systems, building-integrated vs. rack-mounted systems, residential vs. utility systems, vs. centralized systems, rooftop vs. ground-mounted systems, tracking vs. fixed-tilt systems, and new constructed vs. systems. Other distinctions may include, systems with microinverters vs. central inverter, systems using vs., and systems with modules. About 99 percent of all European and 90 percent of all U.S. solar power systems are connected to the, while off-grid systems are somewhat more common in Australia and South Korea. PV systems rarely use battery storage. This may change, as government incentives for distributed energy storage are implemented and investments in storage solutions gradually become economically viable for small systems. In the UK, the number of commercial systems using battery storage is gradually increasing as a result of grid constraints preventing feedback of unused electricity into the grid as well as increased electricity costs resulting in improved economics. A typical residential solar array is rack-mounted on the roof, rather than integrated into the roof or facade of the building, which is significantly more expensive. Utility-scale are ground-mounted, with fixed tilted solar panels rather than using expensive tracking devices. Crystalline silicon is the predominant material used in 90 percent of worldwide produced solar modules, while its rival thin-film has lost market-share. About 70 percent of all solar cells and modules are produced in China and Taiwan, only 5 percent by European and US-. The installed capacity for both small rooftop systems and large solar power stations is growing rapidly and in equal parts, although there is a notable trend towards utility-scale systems, as the focus on new installations is shifting away from Europe to sunnier regions, such as the in the U.S., which are less opposed to ground-mounted solar farms and cost-effectiveness is more emphasized by investors. Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics is declining continuously. There are several million PV systems distributed all over the world, mostly in Europe, with 1.4 million systems in Germany alone – as well as North America with 440,000 systems in the United States. The energy of a conventional solar module increased from 15 to 20 percent since 2004 and a PV system recoups the energy needed for its manufacture in about 2 years. In exceptionally irradiated locations, or when thin-film t. This section includes systems that are either highly specialized and uncommon or still an emerging new technology with limited significance. However, or off-grid systems take a special place. They were the most common type of systems during the 1980s and 1990s, when PV technology was still very expensive and a pure niche market of small scale applications. Only in places where no electrical grid was available, they were economically viable. Although new stand-alone systems are still being deployed all around the world, their contribution to the overall installed photovoltaic capacity is decreasing. In Europe, off-grid systems account for 1 percent of installed capacity. In the United States, they account for about 10 percent. Off-grid systems are still common in Australia and South Korea, and in many developing countries. Concentrator photovoltaics (CPV) and high concentrator photovoltaic (HCPV) systems use or curved mirrors to concentrate sunlight onto small but highly efficient solar cells. Besides concentrating optics, CPV systems sometime use solar trackers and cooling systems and are more expensive. Especially HCPV systems are best suited in location with high solar irradiance, concentrating sunlight up to 400 times or more, with efficiencies of 24–28 percent, exceeding those of regular systems. Various designs of systems are commercially available but not very common. However, ongoing research and development is taking place. CPV is often confused with CSP () that does not use photovoltaics. Both technologies favor locations that receive much sunlight and directly compete with each other. A hybrid system combines PV with other forms of generation, usually a diesel generator. Biogas is also used. The other form of generation may be a type able to modulate power output as a function of demand. However more than one renewable form of energy may be used e.g. wind. The photovoltaic power generation serves to reduce the consumption of non renewable fuel. Hybrid systems are most often found on islands. island in Germany and island in Greece are notable examples (both are combined with wind). The Kythnos plant has reduced diesel consumption by 11.2%. In 2015, a case-study conducted in seven countries concluded that in all cases generating costs can be reduced by hybridising mini-grids and isolated grids. However, financing costs for such hybrids are crucial and largely depend on the ownership structure of the power plant. While cost reductions for state-owned utilities can be significant, the study also identified economic benefits to be insignificant or even negative for no. The cost of producing photovoltaic cells has dropped because of in production and technological advances in manufacturing. For large-scale installations, prices below $1.00 per watt were common by 2012. A price decrease of 50% had been achieved in Europe from 2006 to 2011, and there was a potential to lower the generation cost by 50% by 2020. Crystal silicon have largely been replaced by less expensive multicrystalline silicon solar cells, and thin film silicon solar cells have also been developed at lower costs of production. Although they are reduced in energy conversion efficiency from single crystalline "siwafers", they are also much easier to produce at comparably lower costs. The table below shows the total (average) cost in US cents per kWh of electricity generated by a photovoltaic system. The row headings on the left show the total cost, per peak kilowatt (kWp), of a photovoltaic installation. Photovoltaic system costs have been declining and in Germany, for example, were reported to have fallen to USD 1389/kWp by the end of 2014. The column headings across the top refer to the annual energy output in kWh expected from each installed kWp. This varies by geographic region because the average depends on the average cloudiness and the thickness of atmosphere traversed by the sunlight. It also depends on the path of the sun relative to the panel and the horizon. Panels are usually mounted at an angle based on latitude, and often they are adjusted seasonally to meet the changing solar . can also be utilized to access even more perpendicular sunlight, thereby raising the total energy output. The calculated values in the table reflect the total (average) cost in cents per kWh produced. They assume a 10% total capital cost (for instance 4%, 1% operating and maintenance cost, and of the capital outlay over 20 years). Normally, photovoltaic modules have a 25-year warranty. Photovoltaic systems demonstrate a learning curve in terms of (LCOE), reducing its cost per kWh by 32.6% for every doubling of capacity. From the data of LCOE and cumulative installed capacity from from 2010 to 2017, the learning curve equation for photovoltaic systems is given as • LCOE : levelized cost of electricity (in USD/kWh)• Capacity : cumulative installed capacity of photovoltaic systems (in MW)