How to determine if my heating & cooling system is adequ

Is there some kind of calculation I can follow to determine if the heating and cooling system in my home is rated (adequate) for the size of the house?

I assume there is some way to say something like “for X square feet per floor you need Y kind of system” for heating and cooling.

I recently bought a house (basement + 2 floors - ~1020 square feet per floor excluding garage) and I have the following system:
- Rheem heat-pump (Model - RPLB-030JAZ) which is rated as 30,000 BTU/HR (8.79 kW)
- Amana 15 kW Electric Furnace (Model – MBR1600AA-1AA)

So, trying to determine if this system is sufficient (or not)…
Thanks,

To do such a calculation you need information on thermal conductivity of walls, floor and roof, desired internal temperatures with respect to outside temperature, air transfers and leakage though doors, windows, wall, roof etc, the list goes on. An IR survey of the house to determine hot spots would also be of assistance
Without such information it's a case of "it's cold outside am I warm inside"
Or in the case of summer, "it's warm outside am I cool inside"

Don't forget to factor in a ventilation-obsessed wife who leaves all the upstairs windows open all day then forgets to close them when the heating starts up.

But when we buy such a system, how do they determine what you need? I doubt the company will spend time and money on a barrage of tests - so how do they determine it? I had assumes it was simply based on the home square footage - at least for a good approximation.