@Wolfgang: Voltage drop would be a big issue with 24V. I know a guy who runs his house on solar panels only, and he wired his 24V ceiling lights with 6mm2 - that's ridiculous. Besides, most small appliancess use all kinds of queer voltages inside, so they'd need a DC-DC converter like a chopper anyway. So I think a Switching mode power supply or good old transformer from 230 to whatever voltage is needed is still the better option.
