i've been wondering this as well. like, if i have a 4000w inverter that is supplied by batteries and puts out 240 split phase to a normal breaker box, but let's say i want to run an 8kw instant hot water heater for 15 minutes... could i stack 3 of the 4000w inverters in parallel, so that they could potentially put 12kw into the breaker box supplying the hot water heater? 15 min of use is only 2kwh draw from the battery which is going to be not even 1% of capacity.
and would i have the added redundancy of if one failed, i still have 2 running, which might not handle the water heater, but would still run every other load