Is this 1GW theoretical output or 1GW actual since solar cells are typically only 25% efficient in the best conditions.
I'm not sure what you mean by theoretical vs actual.
Solar panel installations are typically rated by
nameplate wattage, which is the power produced under a standard set of test conditions (STC). PTC is another common wattage rating, it's a more realistic gauge of power in real-world conditions and typically 10-15% less than STC.
Gigaom's source is SolarCity's 4Q 2014
shareholder letter.
After eight years of investment, execution, and growth, we have built a formidable base of distributed solar energy systems across the country. Since installing our first rooftop solar system in 2006, we have deployed 1.1 GW of solar— one of the original goalposts for the company and a significant milestone for us and the industry as a whole. In aggregate, our portfolio of solar energy systems exited 2014 producing clean energy at a run rate of approximately 1,500,000 Megawatt-hours [MWh] per year, and we plan to double that in 2015. With end-market demand healthy and growing, our installation capacity steadily ramping, and a majority of our financing needs secured for the year, we remain confident in achieving our guidance to deploy 920 – 1,000 MW in 2015.
Definitions:
“MW†or “megawatts†represents the DC nameplate megawatt production capacity
Note that they specify DC nameplate, which is power before it goes into inverters to produce AC grid power.
