According to a new report by NPD Solarbuzz, solar photovoltaic (PV) installations in the U.S. have broken through the 10 gigawatt (GW) barrier. During the first half of 2013, more than 1.8 GW of new solar PV capacity was installed according to the North America PV Market Quarterly report.

So, per the DoE's EIA, we just need to install enough additional solar panels to generate 956 GW of energy - roughly $3T (including the land).

The North American Electric Reliability Corporation (NERC), the electric reliability organization certified by the Federal Energy Regulatory Commission to establish and enforce reliability standards for three major electrical interconnections serving the United States, issues a reliability assessment each year. NERC estimated in November 2012 that the United States would have 966 gigawatts (GW) of electric supply capacity available for the summer of 2013. NERC estimated that about 786 GW would be needed to meet projected peak electricity demand and determined that another 117 GW should be available in case of supply outages or extreme weather (known as target reserve supply).

The United States has 63 GW of capacity above and beyond the NERC target reserve supply. The level of above-target capacity varies by region: some areas have significant excess capacity and others are more constrained. ERCOT, the region that makes up most of Texas is of particular concern and is projected to be below target capacity for the summer of 2013 forward. Because of the layout of the electric transmission grid, excess resources in one region cannot necessarily be used to make up for a deficit in another region (ERCOT is particularly limited when it comes to importing electricity).

The electricity industry has reserve capacity on hand to maintain reliability. Because large-scale electricity storage is not currently economic, electric systems must have sufficient supply resources available to meet electricity demand and replace unexpected losses of supply. Each NERC region has a reserve margin target—the amount of supply capacity over and above a region's expected hourly peak demand for the year needed for reliability. The NERC regions' reserve margin targets typically range from 14%-17% and together total 117 GW of supply capacity.