Sizing for One Big Outage vs. Sizing for Frequent Short Ones
Someone planning for a rare but potentially multi-day outage (a major storm season, for example) generally needs a larger single capacity to run essentials for several uninterrupted days without recharging, while someone dealing with frequent but brief outages (an unreliable grid with many short blips) can often get by with a smaller capacity that simply gets recharged between events — the total watt-hours needed per event matters far more than the number of times you expect to use it.
These are genuinely different planning scenarios, and conflating them leads to either overspending or under-preparing.
Planning for the rare, extended event
If your main concern is an infrequent but potentially days-long outage (major storms, regional grid issues), sizing needs to assume no recharging opportunity for the full expected duration — this is exactly the multi-day calculation the Power Station Size Calculator handles, using your device list and the days-of-backup slider.
Planning for frequent, short interruptions
If outages in your area are frequent but typically brief (an hour or two at a time), a smaller power station that's kept topped up between events, or paired with solar for daytime recharging (as covered in the Solar Charging Time Calculator), often meets the real need without paying for capacity that mostly sits unused.