So solar panels produce DC current, no conversion actually happens when sunlight is generated as electricity.
The DC current is then converted to AC as it is efficient in the electrical grid for long distances. However it is also used at home and majority of devices (hardly at least) don’t use AC as it gets converted to a safer DC current. This is especially important for electronics and battery recharging. When conversion happens, majority of that energy is lost as heat which you would find in the charging brick. In addition, with smartphones and EVs, wouldn’t direct DC be more efficient and quicker to charge than converting it back to DC. [Proponents claim that it would be beneficial if buildings had a ‘AC-DC converter box’ near a switchboard.](https://www.youtube.com/watch?v=hF_A4sp7nM8) (should mention that this is not a very credible source but others also claim similar stuff with DC)
So as I said before, why is AC forced as the current for homes instead of direct DC. Only current that needs to be exported to the grid would benefit from AC conversion. I couldn’t really see any answer to this with solar on mind. They will say AC is used for powering things while the other sites claim that AC burn devices if used.
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A 12V 100A DC cable is a chunk thicker than a normal mains cable, despite not being able to carry the same amount of power (volts x amps) as one.
The higher the voltage, the more power you can carry on a thinner cable. So 110/220V around the home means I can – in my country – pull 3.5KW in a cable that isn’t even as thick as the one that comes from a single 150W solar panel.
You don’t want to see how thick a cable has to be to connect to any substantial battery bank for DC. Nor how short you need to keep it to stop it overheating or having too much voltage drop.
So transforming to high voltage is certainly something you want to be doing.
DC vs AC, however, is less clear.
Because you want to transform the voltage (from 12 to 110/220V), it’s actually easier to do that with AC than with DC. And if you want to transmit it any significant distance – even around a home – AC has less loss.
AC is far easier to generate for mains supply because you can use a rotating device to translate really well to AC. Hence even a wind turbine will be better suited to AC than DC in a small home system. Solar is relatively unusual in being DC generating.
Thus solar generating low-power DC is actually the oddball and subject to problems. Thus the very first thing we want to do with it is turn it into high-voltage AC. And that’s what inverters do.
The fact that “AC battery storage” isn’t really a thing also means that battery banks tend to be DC.
So it’s better to have all the low-voltage DC generation/storage in one place, convert that up to high voltage AC as best and as soon as you can, and then use that for EVERYTHING else (i.e. your entire home). EVEN if that means transforming it back down to low-voltage DC (like a USB plug). The losses in those kinds of low power situations aren’t worth worrying about. But when you turn on your high power electric heater or cooker, on the opposite side of the house to the solar battery bank, you’ll want to do it with high-voltage AC for as much of that distance as possible. Because the losses are the same as the above example, in terms of percentage, but the power FAR higher (meaning the overall losses would be far higher).
It’s almost like people sat and worked this out over hundreds of years and arrived at the best compromise all round – low voltage DC is transformed to high voltage AC when going any distance, high-voltage AC is transformed to very high voltage AC when joining towns or crossing the country, and then in the home if we need to we get it all back down to low-power DC for some small, low-power applications but otherwise use high-voltage AC for anything that pulls serious amounts of power (cookers, heaters, etc.).
Those big wall plugs that power your appliances from the mains – they are converting from high voltage AC back down to low voltage DC at the VERY LAST MOMENT before you put them in an appliance. Because that’s the most efficient way to do that.
It means your home has dozens of AC->DC convertors in it, whether you realise it or not. You could say “why not just run 12V / 5V DC around your home… same reasons. It’s actually simpler, cheaper, easier and less loss to run everything on AC and then down-convertor and transform to DC at the very last minute than try to deal in entirely DC cabling and circuits unnecessarily.
In my (rather primitive) home solar panel setup, the leads between my batteries and my inverter are 20cm long and about 1cm thick copper. They get warm if I pull a lot of power.
The leads from the inverter to everything else are 220V AC, and they are just bog-standard ordinary mains leads (so barely a few mm thick copper each) and I can use them at the other end of a very long extension cable if I so wish, or run a high-power heater off them without them getting warm.
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