I guess you could pick whatever voltage you want for your loads and cable runs, but you need to have the appliances you want available (or easily DIY) in that voltage. It would probably be possible to convert down the voltage once, but any more than that and you're introducing loss again.
In other words, a 120VAC LED should work just fine on 48VDC with the same output.
It’s also explains why they don’t dim.
(Obviously avoid the dimmable ones in this application!)
It is putting more current through each light.
And particularly problematic if each bulb has parallel LEDs and they start burning out: then more and more current is put through the remaining LEDs.
You still need PWM to control brightness, no? I'd you're using resistors efficiency goes down a lot.
12 volt wiring in homes isn't terribly efficient as once you get past 6-10 feet you need really expensive (heavy, thick) wires to not have much voltage drop. Most new boats use 24 or 48v for long haul and then local step down to 12v where needed (kitchen, living, sleeping areas etc).
He still has all the original 110 wiring and fixtures in the house, but this battery-backed solar system runs all his lights. It can easily go 2 days without sun before he needs to use the regular lights. Another benefit is that DC LED bulbs are by definition flicker-free, and also low consumption (4-6 watts each) but bright. He calculated he can light each room better than before with 6-8 bulbs, so 40-50 watts, thus only 4-5 Amps (@ 12 VDC) to each room.
All the big appliances in the house still run off of of AC, but he does have a 110 inverter so that he could run a critical appliance such as a fridge during an extended outage.
So this little system replaces 1-2 kWh of incandescent lighting per day (CFC or LEDs on 110 would be less, but not flicker-free), while providing lights during outages. He says it's not cost-effective (the usage displaced by solar and battery usage doesn't cover the cost of the system), but the backup powers is worth it to him.