It's further down my list, but I am starting to investigate adding DC circuits to my house. Between solar and battery backups it would make sense to run as much as possible off of 12V DC.
Modern inverters and efficient walwarts (thank you EU) will be more efficient than 12v DC because of the power lost to the cables for anything but trivial loads.
The problem is some squared math functions which come and bite you. Your 12V DC system will pull 10 times the current as a 120V AC system. That's going to mean bigger wire. But then the kicker comes in, each volt you drop means 10 times the energy loss because 11/12 is a lot worse than 119/120, so you'll have even bigger wire. My 24V system with the batteries in a shed has $900 of copper wire between there and the house.
Then consider that all your loads probably already have a voltage converter in them, either an AC-DC external converter or something internal. Most of them won't take 11-14VDC inputs with spikes on it, so you'll need DC-DC converters on them anyway, so you aren't saving the conversion losses on the device end.
In summary, with modern high efficiency inverters you will probably find that your dollar is better spent on solar panels and batteries than masses of copper wire. If I were starting in 2018 I would not have run the DC lines.
If an AC inverter doesn't provide a sine wave, some equipment will fail. Making the sine wave is a serious burden, drives up the cost, and doesn't make efficiency any easier. In my case the DC cables are a few feet long.
Have you had to replace your batteries yet? I’d assume batteries are a recurring (if with a long period) expense, while wire is a one-time cost. Does the downward trend in battery prices still kill any consideration in that direction?
There still might not be enough power loss to matter, but even with 70-80% efficiency you're still talking an extra 25-50% batteries over the ideal.
If you are using it to power a very light load, the efficiency will be much worse, as it takes a minimum amount of energy to run the inverter.
DC power lines are also better underground or undersea, they don't suffer from the capacitance to the surrounding material.
The AC-DC conversion equipment at each end has a cost, but for 300 mile aerial lines or 30 mile underground lines it is currently cheaper to do DC.
DC is much less workable at low voltages like 12v or 5v common in household application -- the P=IV equation is more dominated by current, so with more current the resistive losses add up quickly even in a run across your house (it'll be down to 10 or 8v by the time the wire reaches the far end of your house). Not to say some people haven't suggested wiring homes with 12v lines... data centers have implemented (or at least experimented with) DC distribution due to the density of DC devices.
Also there's always capacitance which will cause some loss for AC but of course capacitance won't affect a DC transmission line. HVDC also makes combining different electrical grids extremely simple as there's no phase difference or frequency difference to worry about. DC also requires lower peak voltages as AC is going to be sqrt(2) times higher than the rms voltage.