Looking at new automatic standby generators for a livestock site.  One big enough to run everything is well over $30K.  I can get a 12KW Winco with auto transfer switch for under 6K.   I would have to isolate the circuits  I would want to function in an outage with a separate panel so as to not overload it.

I'm wondering if it is possible to put some sort of switch on the circuits that I would not want to energize after an outage so that after the power goes out and the generator starts, the extra circuits stay off until I turn them on.  This way only the necessary circuits run during the outage on a smaller generator and I don't have the expense of adding a separate emergency panel and running wires from multiple barns to the second panel.