“You don’t need or want a separate transfer switch. You are installing what we call a "whole house" inverter that will power the entire panel. Yes you can run the air conditioner, microwave, electric water heater, electric fridge if you like... not all at once and only until the battery is dead.”
In general I do agree with this ”You don't need or want a separate transfer switch” as it is the simplest method of install, but will require that the inverter be ON to allow shore power to pass thru, and a charger to be ON (whether inverter-charger or OEM charger) to resolve the 3.5a parasitical drain...Upon reflection (memory now re-awakening - lol) the main reason we went with a secondary ATS Switch was due to having Lifepo4 batts, and having no desire to leave them under a constant charging ON source - eliminating the parasitical battery drain (via second ATS install) solved this nuance...
Be advised that to electrically heat a single batch of 6gal of water (via an inverter) will take over 1400w of battery capacity (about 110a/hrs)...Thus when off-grid, the heating of water, electric-resistance type refrigeration or heating, and air conditioning are uber inefficient, and this is why some folks opt for a sub-panel (as depicted in the illustration you previously provided) to sequester these loads away from the inverter...
