Space for panels is very constrained, they already get in the way more than I'd like.

I'll probably expand the battery bank at some point, but that only averages energy over a wider time period rather than increasing the total available.

I've spent very little on 12V equipment - my router and laptop are easily run off DC-DC supplies and USB supplies/lighting/water pumps/radios etc. are widely available. The only thing that's powered full-time and would have been significantly more expensive at 12V is the fridge, and I got that for free with an easily-replaced failed thermostat.

Doubling my present battery capacity would definitely cost more than I've spent on everything else.