Outages in Hawaii are not rare, and the gap between a house that copes and a house that does not is almost always the transfer switch, not the generator.
Why the extension cord method is dangerous
Two shortcuts turn up constantly. The first is running individual extension cords through a window, which is only a trip hazard. The second is a suicide cord, a double-male lead plugged from the generator into a dryer or range outlet to backfeed the house.
Backfeeding energises your service conductors, which means it can energise the utility line outside. That endangers line crews working to restore your power and anyone near a downed conductor. It also means nothing protects your generator when utility power returns.
Transfer switches, plainly explained
A transfer switch physically prevents the generator and the utility from being connected at the same time. That is its entire job, and it is not optional.
A manual transfer switch or a breaker interlock kit is the affordable version. You start the generator, flip the interlock, and turn on the circuits you want. It costs less and it works, provided someone is home to operate it.
An automatic transfer switch senses the outage, starts a standby generator, and switches over within seconds. That matters if the property is often empty, if you keep medication cold, or if anyone in the house depends on powered medical equipment.
Sizing: whole house or critical loads
Whole home backup is the most expensive path and often unnecessary. A critical loads panel covering the fridge, some lighting, fans, internet, a well pump and a couple of receptacles is dramatically cheaper and covers the actual discomfort of an outage.
Air conditioning is what pushes people toward large units. If you can live with fans for a day or two, your generator gets much smaller and much cheaper.
Installation details that matter in Hawaii
Pad placement clear of windows and vents, with the manufacturer's clearances respected. Corrosion-appropriate hardware. A conduit route that will not sit in standing water. Exercise scheduling so the unit actually starts when you need it.
An unexercised standby generator is a decoration. Set the weekly self-test and have the transfer switch load tested annually.
Battery backup as an alternative
Battery storage paired with solar is silent, needs no fuel, and handles short outages very well. Multi-day outages are where a fuel generator still has the advantage. Plenty of homes end up with both, with the battery covering the common case.