On paper the numbers look right, but a week off _50kWh_ EV battery feels off.
What follows is back of the napkin calculations, so please treat it as such and correct me if I am wrong.
1. Inverters are not 100% efficient. Let's assume 90%
2. Let's also assume that the user does not want to draw battery to 0 to not become stranded or have to do the "Honda generator in the trunk" trick. Extra 10%?
3. 300W continuous sounds a bit low even with gas appliances. Things like the fridge and furnace blower have spiky loads that push the daily average. Let's add 100W to the average load? I might be being too generous here, but I used 300W, not the 200W lower bound.
4. Vehicle side might need some consumption. If powering off the battery, it would probably need to cool the battery or keep some smarts on to make sure it does not drain or overheat? Genuinely not sure how to estimate this, let's neglect it for now.
Math is (50kw - 10%(inverter loss) - 10%(reserve)) / 0.4 = 100 (hours), ~ 4 days.
The above calculations assume a sane configuration (proper bidirectional wire, not suicide cord into 12v outlet). Quick skim of search for cars with bidirectional charging support for home shows batteries between ~40kWh(Leaf) to 250 kWh (Hummer).
So looks like one should be looking for ~80kWh battery, which actually most of the cars in the list have.
Again, very back of the napkin, would probably wanna add 20% margin of error.
Actually yes one thing I didn't consider in my calculation is the fridge (mostly because it's a spiky load that rarely comes on and I based it off my own apartment's instantaneous consumption at the time which was ~100W since the fridge compressor wasn't running).
Indeed with the fridge it pushes it a bit. But to address some of your other points:
> it would probably need to cool the battery
I'd expect if you're in a storm then you probably don't need any cooling - not to mention a 300W load is nothing for an EV battery compared to actually moving the vehicle. I'd expect some computers in the vehicle to be alive but that should be a ~10-20W draw.
On the other hand, my calculation assumes ~300W continuous. I expect the consumption to lean into the evenings due to the extra lighting, and drop off during other times.
But yes 80kWh might very well be what the OP has; I intentionally picked 50kWh as the lowest option I found on a "<major ev brand> battery kwh" search.
What follows is back of the napkin calculations, so please treat it as such and correct me if I am wrong.
1. Inverters are not 100% efficient. Let's assume 90%
2. Let's also assume that the user does not want to draw battery to 0 to not become stranded or have to do the "Honda generator in the trunk" trick. Extra 10%?
3. 300W continuous sounds a bit low even with gas appliances. Things like the fridge and furnace blower have spiky loads that push the daily average. Let's add 100W to the average load? I might be being too generous here, but I used 300W, not the 200W lower bound.
4. Vehicle side might need some consumption. If powering off the battery, it would probably need to cool the battery or keep some smarts on to make sure it does not drain or overheat? Genuinely not sure how to estimate this, let's neglect it for now.
Math is (50kw - 10%(inverter loss) - 10%(reserve)) / 0.4 = 100 (hours), ~ 4 days.
The above calculations assume a sane configuration (proper bidirectional wire, not suicide cord into 12v outlet). Quick skim of search for cars with bidirectional charging support for home shows batteries between ~40kWh(Leaf) to 250 kWh (Hummer).
So looks like one should be looking for ~80kWh battery, which actually most of the cars in the list have.
Again, very back of the napkin, would probably wanna add 20% margin of error.