This is a seriously good idea, but if you do the sums then most people will need far, far more solar panels than they show, just to power the everyday DC devices they have around.
I've been thinking of doing something similar, putting a low voltage DC supply around the house to power things like routers, the cable modem etc, and the LED lighting I've already installed in the workshop. I happen to have 200W of solar panels on the boat, that just sit on the drive doing nothing 99% of the time, so I would very much like to get hold of some cheap batteries and give it a go.
The off putting thing is the need to re-wire part of the house to put the low voltage system in, plus the fact that even my big 200W array probably wouldn't be enough to run the wireless router and cable modem all the time, let alone anything else. In practice, a 200W array here in the South of England delivers around 120 watts peak, maybe 50 to 60 watts average, for an average of less than half of any 24 hour period, so maybe 25 watts around the clock, maximum, probably less during the winter.
Jeremy