In 2009, Southern California Edison entered into a contract with Solar Millennium to purchase solar thermal power up to 726 MW. Southern California Edison also entered into a contract with Stirling Energy Systems to buy electricity from a 500 megawatt, 4,600 acre (19 km2), solar power plant which was due to open in 2009. The purchase was canceled in late 2010, as changes in technology reduced the cost of photovoltaic-based solar power to below that of solar Stirling generated power. This would have been the first commercial application of the dish stirling system. A different technology from the more familiar solar panel, the dish concentrates solar energy by the use of reflective surfaces and by the use of the Stirling heat engine to convert the heat into electricity.