Ok, in my former business I was a electrical & HVAC contractor. In my time I have come across numerous generator installs that were not to code. The installation requirements is fairly simple on a generator. Any generator installed after 2008 must meet this requirement as it is the same in both 2008 and 2011 code books.
If you read the 2011 NEC Article 702 it covers optional stand-by system. In simple words 702.4 says that a generator must carry the entire load that is transferred to it by automatic means, if the generator cannot carry the whole load it must have load shedding installed. Load shedding is as simple as installing modules that interrupt the power going to high wattage appliances such has the HVAC, Waterheater, Dryer, Pool systems and such.
If the generator has a selected circuit automatic transfer switch then it must be able to carry all the loads that are wired to the selected circuit panel. This panel would be mounted next to the main panel and ether be a combination transfer switch or be a standard panel that is connected south of a standard transfer switch.
Combination Transfer Switch
Sub Panel with Standard transfer switch
If the generator automatic transfer switch is connected in-between the meter base and the main panel then it is transferring the whole load of the house.
Transfer switch mounted in-between meter and main panel
You can calculate the total load of the house by using this work sheet www.piertopier.us/hvac/RCO_Automated_Rev2.xls if the generator puts out more amperage than you get from that work sheet then the unit meets NEC 702.4
If the generator puts out less amperage than you get from that worksheet then it is required that high wattage appliances have a load shedding module installed to turn them off if the generator gets over loaded.
Generac load module
Do any of you currently look for this, or do you think this should or should not be looked at by a home inspector.