In some countries, the nameplate capacity of photovoltaic power stations is rated in megawatt-peak (MWp), which refers to the solar array’s theoretical maximum DC power output. In other countries, the manufacturer states the surface and the efficiency. However, Canada, Japan, Spain, and the United States often specify using the converted lower nominal power output in MWAC, a measure more directly comparable to other forms of power generation. Most solar parks are developed at a scale of at least 1 MWp. As of 2018, the world’s largest operating photovoltaic power stations surpassed 1 gigawatt. At the end of 2019, about 9,000 solar farms were larger than 4 MWAC (utility scale), with a combined capacity of over 220 GWAC