Things fall apart, fade to black
There are some people who believe that once they go on solar electric power, the grid can go down and they are set forever. Those of us with actual real world experience know better. Eventually, things have to be replaced. Most high quality solar electric panels are warrantied for 20 - 25 years. I doubt the companies pay out very often. There's very little that can go wrong on a solar panel. My grandkids may get mine.
Batteries are another matter. The very best batteries you can buy may go as long as 30 years, with proper maintenance. Very few people actually own those batteries as they are outrageously expensive. Most people use different varieties of lead acid batteries. They work pretty well for the money involved. I use Interstate golf car batteries, take good care of them, and get about 10 years of service. My first set I did every mistake in the book and got about 7 years. Probably should have changed them at 6.
My home inverter has lasted 20 years and is still going strong. It was expensive, but quality only hurts once. In my truck I've been using cheap 2000 watt inverters from Harbor Freight. To be fair, bouncing around in a truck is a harsh environment, but I fried an inverter in 2.5 years.
I've replaced a charge controller, but the old one was still working after 18 years. I've heard of cheap ones burning out in months. Quality matters. Solar electric systems vary quite a bit in their complexity, but just assume that every single part can eventually fail. Some failures won't shut the system down, but other's will. If my electronic battery monitor quits, it's a bother, but the system still works. Instead of glancing at a meter on the wall, I have to pull the battery caps and check with a hydrometer. You do have a hydrometer don't you? (and eye protection and rubber gloves)
A solar electric system is great for when the grid goes down for a few hours, days, weeks, and maybe even a few months. If the grid goes down for much longer than that, something is seriously wrong and electric power probably won't be your biggest worry.
Something else to consider. In an emergency, your usage will be different. We had an ice storm that took down the grid over a large area. Some people lost power for several weeks. I only lost grid power for 4 days. Here's what happened. Lots of people came over to my house. The place filled with my kid's friends and they watched a lot of movies. People came over to fill water jugs as their well pumps didn't work. Friends came over to take showers. At the end of 4 days one of three things had to happen: the sun would have to come out again, the grid would need to come back on, or we were going to seriously conserve electricity. As it happened, the grid came back and the sun came out at the same time.
In a crisis situation, your solar electric system will probably work harder than it normally does. During the ice storm, my batteries drained lower than I normally let them get. Do that sort of thing too often and they need replacement sooner.
In a lot of countries, electric power isn't a 24/7 thing. People work around it. The US grid is stressed in a lot of places and could become less reliable. It seriously needs major upgrades just when money for those projects has become harder to get. That's were having some backup power is nice. It won't last independently forever, but it's useful for everything less than that.
Gas, diesel, or propane generators work just fine to bridge those times when the grid goes down, but they don't get refueled by the sun. During the big ice storm, a lot of people had generators that ran out of fuel in 12- 24 hours. Gas station's fuel pumps didn't work without electricity either. Plus, the roads were icy and covered with fallen trees. If you are going to go with a generator, make sure you've safely stored enough fuel for more than a few hours.
While solar electric systems may go years without major problems, few generators can handle constant use. Cheap generator's lifespans are measured in hours. If buying a generator for heavy duty use, expect to pay thousands, not hundreds of dollars. It's that math that persuaded me to spend the money on solar instead. Well, and the fact that I'm lazy and hate to fuel and maintain a generator.
For all the things that can go wrong with a solar electric system, it's surprising how trouble free they usually are. They won't last forever without maintenance, but nothing in our technological society does.
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