There are better ways to spend your money to cover risks than batteries. Maybe if you were getting a battery for other reasons, or as a luxury if you are wealthy enough.
12-24 hours would have outlasted any outage I've experienced, until I moved to my current place, but it has a propane fueled whole house generator (and low utility rates with no time of use component; i haven't attempted the math, but I'm pretty sure running from my generator is way more expensive than utility power... OTOH, I've had many utility failures and only one generator failure (12v battery failed due to charger failure))
There is little point worrying about marginal efficiency when power is out because saving a few dollars over a few hours is not worth optimising for. - High fixed costs (batteries & inverter) would dominate small operating costs (propane, wear&tear).
Probably not worth it though at the moment. I suspect it would be simpler and lower cost to double my fuel storage capacity. Lived experience says in 6 years, the maximum duration outage was less than 3 days, and my storage capacity is plenty good for that.
> the maximum duration outage was less than 3 days
Past performance is no guarantee of future results!
My semi-rural parents were at one end of the faultline of the Canterbury earthquake and my sister lives on a rural property on top of the Kaikoura earthquake.
If you are in an earthquake zone, my lived experience has been that planning for more than a weeks disruption is very worthwhile.
They both have wood burners and had months of firewood so heating was fine. They used gas cookers for a while. Both have septic tanks and both had non-powered water supplies (no electric powered wells - they had tanks fed from roof and hillside). I think my sister lost a couple of chest freezers of meat because power was out. Many people had no serviced power for an extended period of time. My sister lost their ADSL internet (their property has zero cellphone coverage). She'd be okay now with her Starlink.
After an earthquake, you cannot buy a generator (they are all sold quickly).
Getting gas deliveries might be difficult (bridges and roads were fucked near my sisters).
I will instal solar with batteries and I live in a city. Power, sewage and water were out in many parts of Christchurch for a long time after the Christchurch earthquake. I'm no prepper. I am just happy to hedge my insurance bets if the price is right!
Then again: after three major earthquakes I would hope we all learn a little...
If you're visiting NZ then come visit.
Batteries are cheap. A 5 kWh battery storage pack can be had for ~1500€ these days, that's enough to ride at least the fridge, freezer and LED lighting for a day or two through a major event. In rural areas, add a small 1-2 kW generator and a transfer switch for another few hundred euros, and now you're completely set even for larger outages.
I found a cheap 5kWh wall unit includes everything for $4,350.00 NZD (things are more expensive at our edge of the world). Median after tax pay in New Zealand is a bit over $52,000 per year. I don't consider nearly a months earnings to be "cheap". Maybe you are just wealthy?
You can use a battery pack not just for emergency storage but also to store energy in cheap times (i.e. at noon) and draw from it at expensive rate times. Of course that requires a variable-rate tariff, but these are getting rolled out even in Europe.
> Plus you are ignoring the cost of a charger and inverter.
Indeed, you're right (my bad, mis-read an offer), but even then - a full system, including battery pack, controller and an inverter that can additionally be fed from a solar panel is just 2.500€.
> I don't consider nearly a months earnings to be "cheap". Maybe you are just wealthy?
Distribute the 2500€ across 20 years of lifetime and it's 10€ a month, and that's before the potential for savings you can get by attaching a solar panel. Yes, a (relatively) large upfront investment if you are in remote places like NZ where everything is expensive, but in Europe or the US? Almost a no-brainer, assuming you have a place to install it.
[1] https://www.fm-solar.de/batteriespeicher/batteriespeicher-pv...
You may not need to do that for long, depending where you live. My wired ISP does not provide service if there's no utility power at their box down the street. The cell towers provide service for about 2-4 hours. And after that, I've got inbound only comms (radio / tv).