The Tesla has a 60 or 85kWh battery. The h is important; it's capacity, not power output. The power output is actually much higher, up to 310kW. But of course that means that if you run it at full bore, you'll only get about 16 minutes out of it. In any case, that kind of power output is vast overkill. A typical house only needs a few hundred watts, and that's easily provided with an inverter on a normal car. So again, I don't really see the advantage here, since both can do the job fine. One major difference is that when your electric car runs out of electricity you are screwed until the power comes back on, while a gas car can potentially be refilled. Even if the gas stations are down, you can stockpile gasoline, while you can't really stockpile electricity.

I know it's kWh. EE, so I get it.

Don't know where you live but "a few hundred Watts" would only power my computers.

I keep a couple of deep cycle 12V batteries fully charged in the garage. We typically use them as power sources for chargin LiPo's for electric model aircraft at the field or to power the glider launch winch. A nice side effect is that the are available for emergency power if ever needed. I still have a 4 kW propane generator because the 12V batteries are simply not enough. I say this from experience not conjecture.

The refrigerator seems like the only real substantial load. I looked that up, and while it'll draw over 1kW when starting, the continuous load is something like 200W for a modern one. Nothing else is in my house is going to approach that. I'm not going to be running desktop computers during an extended outage, and laptops will add a negligible impact. In colder weather I'd want enough power to run the gas furnace, which I imagine is not a ton. Lights can be kept to a reasonable minimum, and you'd want LED bulbs available for all the lights you'd use during an extended outage anyway, and so also won't be a whole lot. Thus: a few hundred watts.

But let's say you need 2kW. (That's not quite double what a normal car can put out, from my quick research. Typical car systems seem to top out around 1200W, give or take.) The Tesla would be able to provide that no problem, of course, but! It'll only do so for about 22 hours before you run the battery all the way down, at which point you have no electricity and no transportation and no way to remedy either until the power comes back on. If you really do need 4kW then your Tesla will last you half a day, which is just about useless. If your needs are low enough that the Tesla battery could last for a couple of days, then you can run off a regular car too.

Hence the propane generator.

:)