Today's solar energy systems account for roughly 1% of electricity in the United States each year. Most of this energy is generated by PV systems, which directly convert solar energy into electricity using a solar cell made of a semiconductor material. The remainder is generated by CSP systems, which focus the direct component of sunlight and collect the heat to power an electricity-generating turbine. PV systems can generate power at costs comparable to traditional sources, but they are only useful when the sun is shining. CSP systems allow solar energy to be stored as heat and distributed as needed, but the levelized cost of electricity from CSP is more than twice that of PV. The FOCUS program seeks to create hybrid solar energy systems, which combine the best elements of both technologies to get the most out of the full solar spectrum, generating both electricity and heat within the same system.