At worst, you need to deal with a roofing problem.
For backup purposes, a generator and some fuel seems to be a lot more bang for the buck.
The back up generator is really compared against the energy storage asset and not the solar array. On a multi-day/weeklong winter grid failure generator is a much safer asset to have to protect the home - even including your loss equation.
2nd - much nicer to not have to waste a paid off asset at year 20.
1. Length that the asset can provide power in a grid failure (multi day isn't possible at this point except incredibly small load profiles). As a buyer of a generator/ESS I want multiple day coverage on grid failure not momentary grid failure. 2. Cost is way too much for the power you get.
You gave some personal experiences, so I will match yours. We had a 6.6kW solar panels, with a 4.8kW battery. We lived in a flood zone at the time, so I got a generator after the second time I dumped the meat in the freezer after loss of power.
With all that in place had the usual episode of weeks of wet weather (the monsoons), became an island, the power is disconnected because houses around us (but not us) are inundated as the power company doesn't like being blamed for killing people. The generator was a fail because it couldn't handle the startup load from the fridge and freezer motors.
I didn't have high hopes for the battery. Boy, was I wrong. Turns out 4.8kW is enough to drive everything overnight except hot water, air-con and 2 hour roasts in the oven. And I do mean everything - lights, TV, internet, cooking (well, fast heating), washing machines using cold water, fridges and freezes. It also turns out that a 6.6kW of solar can bring that battery to full charge during the day, even with blanket cloud cover and pissing down rain.
And to your point - it will happily do that for years, without fuel or maintenance. As for costs - a few days ago I saw 10kW hour battery advertised on Alibaba for $1,200, with 90 day returns. At that price, it will pay for itself in power costs. If you add in an electric car, it's a complete no-brainer as while electricity costs may be very cheap where you live, car fuel costs won't be. If that car is a BYD (it has a 3.6kW household power outlet), you don't need a house battery just for emergencies.
There are very few states in the US where net metering doesn't exist, with California having the NBT (and Arizona and Utah something similar iirc), and Alabama, South Dakota, Tennessee, Idaho, and Texas all have utility-set forms of net metering. Just because California has phased it out and it's a sunny state doesn't mean you can't install a solar roof in Massachusetts and benefit.
The cost of panels is dirt cheap (even with tariffs). You don't need energy storage if you pay $100/month in energy costs, just offset that. Home Depot will install it if you want!