All of the labor has been DIY, and I've got about $9,000 invested in the system components.

Back of the napkin math, at current electric rates, puts my ROI at just under 9 years. If electric rates keep going up, it'll pay back even faster.

Edit: Depending on how you look at it, ROI could be in as few as 1.5 to 2 years. This system is in lieu of a whole house generator that would have cost us about $7,000. Had we gone with that instead, it would never have paid for itself (other than peace of mind) and we would have been perfectly content. So if I'm only considering the price difference between this and the generator, it'd only have to pay back $2,000.

If you enjoy it, it already has.

A hobby pays itself just by enjoying it. I've never calculated how long it will take to pay off my gaming rig

I'm more of a hands-on learner but that can get expensive depending on the hobby haha. For going solar, I'm still very much in progress but definitely on the path to where i want to be.

Basically the first step is to decide what your goal is. Do you want to go totally off grid? Just reduce your electric bill? Have backup power? All/some of the above?

If you only want to reduce your bill, check into what's called grid-tied or "balcony solar". That's the easiest to get started with, but it requires cooperation from the electric company since you're feeding back into the grid. I can't do that here, so I went with a standalone/battery-based system.

Once you identify your goal(s), you'll need to figure out what your "base" load is, and then how much your peak loads are so you know what size system to shoot for. Then you'll need to choose an inverter that can meet those with some extra capacity for unforeseen spikes. I started with a 10KW system, but it's also expandable up to 60 KW( 6 units in parallel). My house only has 100A service, so two inverters would actually give me more power than I can currently get from the power company lol.

For the panels, you can really only expect to get 60-80% of their rated output most of the time. The rated output is under perfect alignment with the sun, at the perfect angle, and with absolutely no obstructions. In practice, you'll never see that. As an example, I usually only get between 3 and 3.4 KW out of my 4 KW system on the best of days. This is normal.

For batteries, they're technically optional depending on your goals. If you just want to shave some money off your electric bill, you can forego the batteries and the inverters will happily mix PV and utility to power your loads during the day. e.g. If you're drawing 1,000 watts and only getting 900 watts from PV, then it'll make up the missing 100 watts from utility power.

I sized my batteries based on my average daily usage plus an extra 10 KWh. We use about 20 KWh per day, so I got two 16 KWh batteries for a total of 32 KWh. That means, if there's no (usable) sunshine at all and we lose power, I can run the whole house for a little over a full day. Any sun hitting the panels will reduce the current draw from the batteries while also charging them if we use less than the PV is producing.

The longest power outage we had was about 29 hours, but if we typically experienced multi-day outages, I might have gone for a larger battery.

I had a much longer reply written up, but it barely scratched the surface. So hope this helps in a general sense but happy to answer any specific questions if I can.

don’t charge devices directly from solar power

Unless your power bank has a built in charge controller, this should also include your power bank. At its core, a power bank is nothing more than a big ass lithium ion (or maybe potassium ion, if it's newer) battery, just like the one in any other device.