As panels become hot, they loose some of their efficiency. Some panels will note this in the specifications as a percentage per number of degrees increase in temp. Obviously older panels will be less efficient than newer ones. It can be pretty substantial too. (10-25%)
I have some solar panels and lithium batteries on a bug out/off grid camper. You need quite a lot of surface area of panels, even with the latest and great technology, to generate enough usable power. Especially when you try and run AC or use it to create heat of any kind.
Most people dont think about the fact that the sun isn't out for 100% of the day, you can't get good power when the sun is at low angles, the panels are never perfectly aligned with the sun and then all that power from the panels has to go through an inverter or a charger before it can be used.
I like solar and lithium, for places that are remote or for setups like my camper that allow me to bug out or run from a hurricane if I have too and not have to worry about gas for generators or power. Otherwise, you are basically just pre-purchasing your power with solar. On the other hand, If you take advantage of one of these goverent programs and get the equipment discounted or for free, that changes things.