Interesting article of plugging an inverter to the 12V battery to power your furnace and refrigerator. I like it. This guy used a 2000 Watt inverter. Any idea how high of wattage you can go from the 12V battery? Tesla voids your warranty if you try to power your home with your electric car battery pack - Electrek
1 or more 4D batteries in parallel would run a furnace blower and fridge for quite some time. A good marine inverter will also act as a constant-volt charger when the shore power comes back on.
The new Hyundai Ioniq 5 will have the ability to extract AC power from it, as will the Cybertruck, and Rivian. I suspect most new EVs going forward will have electrical receptacles for power output. Just seems like a good feature. Heck, the new Ford F-150 hybrid is currently king of the hill for power output (it does it via an integrated generator).
Off the 12v is pretty bad. HV to LV to HV, really inefficient and lots of amps off the 12V system. Plus the entire car needs to be powered up. People should just get a generator or battery power pack made for that.