It depends on costs of components, and I am out of touch, the MPPT regulator as far as I remember alters the supply voltage from the solar panel to get maximum output, and uses switch mode power supply technology to change the output voltage to what the battery requires, and loads are taken from the regulator not direct from battery so it can better ensure battery is fully recharged.
However you can also use a simple zenor diode, like were fitted to motor cycles in the 80's.
So the same solar panel can give vastly different outputs depending on the units connected to it. For my caravan while in storage a very small solar panel was enough to maintain the battery, and use the lights on the odd time, but to use solar panels while living in the caravan they need to be far bigger.
I would look to narrow boat users, they have a problem the engine does not run long enough, so have looked at wind chargers and solar panels to supplement what the engine and odd shore hook up can provide, they have got it down to a fine art living mainly off grid.
My garage I just carry the battery down when I want to use it.