Updated from 1:55 p.m. EDTShares of solar energy-related stocks mostly traded lower Tuesday, despite news that SunPower ( SPWRA) and Xcel Energy ( XEL) will build a solar power plant. The two companies have signed a contract to build a 17-megawatt AC photovoltaic solar-power plant in Alamosa County, Colo. It is the latest in a series of agreements announced by solar energy manufacturers and utilities as more states adopt standards requiring a percentage of electricity to be produced from renewable resources. The plant, which the companies expect to complete by the end of 2010, will be the second-largest high-efficiency solar PV power plant in North America and create about 200 jobs during construction, they said in a statement. Xcel said the plant will use SunPower tracker systems, which tilt toward the sun as it moves across the sky, increasing the amount of energy captured. San Jose, Calif.-based SunPower's shares were down 6.7% to $22.97. Among other solar movers Tuesday: JA Solar ( JASO) finished down 13% to $3.06. LDK Solar ( LDK) was down 7.4% to $6.78. First Solar ( FSLR) closed down 3.7% to $133.12. Canadian Solar ( CSIQ) finished down 8% to $6.45. Suntech Power ( STP) was down 9% to $12.66. Yingli Green Energy ( YGE) was lower by 13% to $6.31.