Photovoltaic system in northern climes to 5.61 kWh/m²/day in the sunniest regions. For large systems, the energy gained by using tracking systems can outweigh the added complexity (trackers can increase efficiency by 30% or more). For very large systems, the added maintenance of tracking is a substantial detriment. Tracking is not required for flat panel and low-concentration photovoltaic systems. For high-concentration photovoltaic systems, dual axis tracking is a necessity. Pricing trends affect the balance between adding more stationary solar panels versus having fewer panels that track. When solar panel prices drop, trackers become a less attractive option. Systems designed to deliver alternating
History of photovoltaic growth History of photovoltaic growth The history of photovoltaic growth includes previous forecast and annual deployment figures by country. Most PV deployment figures in this article are provided by the European Photovoltaic Industry Association in the "Global Outlook for Photovoltaics" report, the "Observatoire des énergies renouvelables" or EurObserv'ER's "Photovoltaic Barometer" report, and the IEA-PVPS (photovoltaic power systems) "Snapshot" and "Trends" report. In 2013, worldwide deployment of solar PV amounted to almost 40 GW (39,953 MW)—an increase of about 35 percent over the previous year. Cumulated capacity increased by 38 percent to more than 139 GW. This is sufficient to generate at