In 2022 the US had ~143 TWh of utility scale solar PV [1]. Utility scale solar PV had a nameplate capacity of ~71 GW [2]. So, the average US capacity factor for utility installations is ~0.25.

Or, for simpler calculations, just multiply nameplate capacity by ~2,000 to get the expected annual generation in Wh.

[1] https://www.eia.gov/electricity/annual/html/epa_04_03.html

[2] https://www.eia.gov/electricity/annual/html/epa_04_03.html