Yes, but only for very small amounts of power, as others have pointed out. A better idea would be to run DC on a select few runs of the existing 14-gauge romex from your breaker box to the rooms they serve. You'd be taking those 110v lines out of service and using them exclusively for DC, but you could pump a lot more power across them than you could across telephone wire. (You still wouldn't be able to run electric heating appliances or big motors or incandescent lights, but pretty much everything else in a modern house would work, modulo the need for switched DC-DC voltage converters.)
