Calculating daily energy production of PV panels
"Average hours" on "Average roof" have no particular bearing on a specific roof located in a specific place. 

Specific places have specific weather patterns, which do have local averages that can be used for estimation that's a lot more relevant. In the USA, roughly 30 years of month-by month data are typically available for some weather station/airport near you, though exactly how "near you" it is will vary and may impact how applicable the data is. But in general, the Southwest USA is a lot more productive than much of the rest of the country.

The Northeast in November is certainly dire, as I know from several years spent facing the possibility that I'd have to install an off-grid system. That was the "design month" for getting storage and array size to be adequate - eventually circumstances changed and the power company became more amenable to providing a grid connection I could afford.

With a typical grid-tie, you get to take advantage of "excess" production on long sunny summer days, rather than having to make enough power even in November, and then having excess power (and no place to send it) in sunny months.

Specific roofs also have specific relationships to trees, other houses, and terrain; and specific orientations and angles, all of which affect the specific amount of power an array on that specific roof in that specific location will produce. There are tools a solar installer may use to assess those details.