If your house is wired with the lights and the outlets on separate circuits (mine is, because I'm an EE and I built the house), you could change out all those lights to low-voltage LEDs and supply 12-24VDC to them and light up your house just fine on the 14-gauge copper romex that's in your walls now. This works because the required current would still be well below the 15A at which the wire is rated. (Getting your electrical inspector to approve it might be another matter, though.)
In some cases, this trick would work for the outlet circuits too because most of the things we plug into outlets now are low-voltage DC wall warts, and they could be replaced with low-voltage DC-DC converters. The problem is that your refrigerator and your dryer are not run by wall warts, so outlets are tougher to convert to DC than lights.
In some cases, this trick would work for the outlet circuits too because most of the things we plug into outlets now are low-voltage DC wall warts, and they could be replaced with low-voltage DC-DC converters. The problem is that your refrigerator and your dryer are not run by wall warts, so outlets are tougher to convert to DC than lights.