If the sun doesn't come out to charge the batteries I have a couple generators, one gasoline and a large natural gas unit. The large generator will charge the batteries in about 4 hours that will last for two days under normal load. To get 2 days out of my gasoline generator I would have to run it for up to 16 hours.
I don't want to make it sound easier than it is, you have to install a battery charger ( I have two) and an inverter, I have two of them too, one is not enough for the whole house when everything is on. It isn't as difficult as you might think, you can buy the components you need and likely find a kit that will have everything you need. Of Course, YouTube is your friend.
I did it all myself except for final inspection I had to hire an electrician to be here when the county inspector came to give me a tag. The inspector asked me if it worked after I showed him it did he gave me the tag.
Money is the problem. You have to pay for all that stuff, I happened to have some extra cash lying around after and investment matured so I used it. It was about 50K up front but by the time the government gave me tax credits it was only about 30K.
So after a decade do I think it was worth it? Absolutely! When I decided to do it electricity cost me four cents a KW but it had been announced that it was going to six cents. Well now it is about fifteen cents.
The majority of the months of the year I only pay the minimum connection fee of about $20. There have been Summer months that have been around a hundred dollars but I have a large house and that is cheap.
I started out with a much larger battery bank, but they were flooded lead acid batteries and I just didn't have the time to take care of them properly and ruined them. that is when I converted over to the nice AGM batteries. The AGM's don't require much attention. I like to travel a lot so that is a good solution for me. A lot of people say get Lithium batteries, yeah, they are nice but they too require a lot of attention and I would ruin them and lose a lot of money.
With the old flooded batteries I had to have them in a box and vent them to outside so I didn't blow up the house from their hydrogen gas they gave off when charging. A few of them actually arced when they got low on water from my mismanagement and blew up. It didn't take much of that to get me to get rid of them.