Recently I came across a new product that I have found to be helpful. This is an LED lamp that looks like an ordinary 60W equivalent lamp (9W actual) that contains an internal battery. The battery charges during normal usage - while the light is on. Then if the utility power fails the internal circuitry detects this and powers the lamp for up to 3 hours (if it is switched on). You can't test it by unplugging the light, it needs to be plugged in when the power fails. I found a 2-pack for under $20 on-line. (Click here to purchase on Amazon - As an Amazon Associate I earn from qualifying purchases.)
As I played around with them I learned a lot. First, they come with a socket and hook with a button switch. This allows them to be used for camping or location specific emergency lighting. The way they detect an outage is to sense the resistance in the electrical wiring of the house, so the switch just shorts the contacts to turn the lamp on.
You can also turn the lamp on by touching the bottom of the lamp with a damp cloth - or your fingers. (You can also do an "Uncle Fester" and put it in your mouth to light it by using your tongue to connect the contacts).
When powered from 120V, they produce 60W equivalent (850 Lumens) of bright warm light. On internal battery power the output drops to 40W equivalent (500 Lumens) which is quite bright and useful in any situation. The battery will last 3-4 hours and you can turn the lamp on and off after a power failure just like a normal light. If it is likely to be a long outage, you could conserve power buy using it sparingly.
I tried replacing lamps in my home with varied success. First, I installed 1 in my kitchen ceiling where I have 4 flood lights, it came on when I turned the lights off. I think this is because it sees the other 3 regular LED lights in the circuit and gets confused. Also it is useless with any remote controlled home automation switch because the internal relay will switch it off when the power fails. Same goes for room occupancy sensors that will turn off when the utility power fails and can't be turned on. So these are most useful when used in table and floor lamps or house lighting circuits with only 1 lamp. I'm also using them in my stairwells and hallways for safety.
If I still lived in California where earthquakes could knock out power I would use them widely as emergency lights. Here in Maine, we get outages often in winter storms and they can last hours to days which is why I have an automatic standby generator that can power the whole property for over a week running on propane. But the generator takes up to 15 seconds to start and these lamps will bridge that gap which I find compelling.