I was reading about someone building a DC house, because this would make solar+battery more efficient. I was wondering what those plugs would look like, but found that there didn't seem to be any standard for DC 120v plugs and sockets. So I thought I'd try to make one, just for kicks:
This is based loosely on the 12v coaxial cable that most AC/DC adapters use. I figured that for 15A it would need to be bigger. It has four pins and so can carry both AC and DC, or 120v and 240v, or...