Hi,
To followup a little.

The link of initial post DOES CONTAIN monthly data.

If select an item in the "History Col." you get annual data. At the top left there is a radio button to select "Monthly data".

There is a wealth of information on this site if interested.

Ng for Electric Power generation actually "peaks" in the summer months [July, Aug.] so must be cooling driven. Shortest days, so lighting/street lighting at minimum. If there is some other "summer activity" that would give rise to this, I cannot think of it.

Looking at Residential:
Peak is Dec. thru March and certainly should be attributable to "heating".

Note:
Home heating would show in Residential due to home gas fired boilers, while Air Conditioning would show under Electric Power Generation.

If anyone knows of a "gas fired" air conditioner, I would be interested in hearing about it !!!

Onward ....
Lee