Guys, Thanks for the comments!
The term "back of meter" comes to us from utility company engineers, and apparently more than one panel can be connected to the back of the meter in a SFR.if the meter socket is less than 20-40 years old (depends on the service area). When I bought my house 20 years ago, there is a 200 amp panel, and a 100 amp panel coming of the back of the meter to supply pool pump, HVAC, etc. Seems to work fine. The key point here is that the sub panel is NOT connected to the existing 150 or 200 amp panel but from the back of the meter. Have a look at this form Duke Energy https://www.duke-energy.com/pdfs/Parallel_Main_Panels_from_a_Single_Meter_Base.pdf
24kW seems to be the right size for the southern part of the US, which is also primarily electric, not gas.