Houses have historically only offered AC power throughout, but I'm wondering if that makes any sense anymore.  If I were building a large addition, or even building a new home from scratch, would it make sense to build with only AC power?  Let's think about the main things we have in the house that use power.   LED lights: the bulbs have to convert the AC to DC.  Why not just use DC to begin with?  Of course this means buying new bulbs, which may be expensive, or altering the existing ones, which may be time-consuming... Laptops, phones, tablets: again, they have to convert to DC power, which seems silly and inefficient.  Of course I'd need DC cords for all laptops... Refrigerators: I don't know what form of power they actually use, but I've seen DC versions available at a much higher price, so this may be one reason to at least not get rid of AC completely.  Maybe.   Those seem to be the main things.  I don't need hair dryers or toasters, and can use gas for most other major appliances.  Now let's say I'm going to try to power the addition (or new house) completely with solar panels.  Suddenly any difference in efficiency has a much more noticeable effect on what I'm paying for the panels.  Would it make sense in this case to use DC for almost everything, if not everything, even if it didn't make sense previously?     * UPDATE *  While at first glance this may appear the same as , anyone who takes the time to actually read both of them can see that they are very different.  That other question is looking toward the past and asking why things came to be the way they are.  My question is looking toward the future and asking if it makes sense to change.  In that sense they are the opposite.  Therefore this question should be reopened.
I'm not sure if there's a better place to ask this or not.   Why, at least here in America, is the standard electrical system set up for alternating current (AC) rather than direct current (DC)? I'm just completing a long-distance move and realizing how many DC adapters I have and how many of my devices require DC power:   All of my guitar pedals. My alarm clock. My external hard disks. My USB car HDD dock.   ... and the list goes on. If we're almost constantly having to use DC adapters to convert AC into DC, why isn't the standard DC, other than because people resist change?
If I've decided to update my SE avatar (in any of the various ways well described in the answer to this ), am I able to return to either the original stock image or previous avatar images I have used? Is there a good equivalent implementation of strptime() available for Windows?  Unfortunately, this POSIX function does not appear to be available.   - summary: it converts a text string such as "MM-DD-YYYY HH:MM:SS" into a tm struct, the opposite of strftime(). Is there some way to embed LaTeX source code in a PDF file? How do I undo 'git add' before commit? I mistakenly added files to Git using the command:  git add myfile.txt   I have not yet run git commit. Is there a way to undo this, so these files won't be included in the commit? Is there a way to have a copy of any message sent from a Gmail account sent to another address?  I've got any messages coming to my address copied to another (see  for one solution, setting up filters is another), but I haven't yet found a way to have outbound messages automatically copied.  Is there a way? How come Mortarboard is bronze and Enthusiast is silver? :   Silver  Enthusiast    Visited the site each day for 30 consecutive days   56.9k awarded Bronze  Mortarboard   Earned at least 200 reputation in a single day      15.4k awarded    It would seem that earning Enthusiast requires almost no effort while Mortarboard is highly non-trivial. This appears to be reflected in the award count (almost 4:1 in favor of enthusiasts).  So, why is the first one silver and the second one bronze?  (A similar question can be asked about Epic vs Fanatic and probably many other). Low Quality Posts you Have Already Flagged I just discovered that it is possible to get a post in the Low Quality Posts review queue that you have already flagged for closing, making reviewing that item impossible. 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So, let's take Skeptics.SE for an example. You can become a trusted user when you acquire 4000 rep., not 20000  I was like, wow, so is it like this because of the lack of users on Skeptics.Se, as in, not so much as Stack Overflow or something?  Why do some sites need less reputation to be a trusted user? As opposed to the generic polynomial form for utilizing the Eisenstein Criterion ($a_nx^n+a_{n-1}x^{n-1}+\dots+a_0\in\mathbb{Z}[x]$ is irreducible in $\mathbb{Q}$) how do we prove that if $p$ is a prime, $x^{p-1}+x^{p-2}+\dots+x+1$ is irreducible over $\mathbb{Q}$? What keeps mass from turning into energy? I understand the energy and mass can change back and forth according to Einstein. It is fluid; it can go from one to the other. So, what keeps mass from just turning into energy? Is there some force holding a subatomic particle together? What keeps mass in it's state? I hope this is not a silly question but I am clueless. Thanks Yesterday I had 3,606 reputation but today I have 3,592.  My profile shows that I lost 6 reputation when a user was removed, but that would put me on 3,600 - 8 reputation has magically disappeared.  Adding up all of my reputation does work out at 3,591 (I'm assuming by default new users have 1 rep, so that would make sense).  Somewhere a reputation change since yesterday isn't being displayed. I don't know what this would be for, but -8 would lead me to believe that someone removed their up-vote on an answer I'd posted which already had a down-vote (could it be from that deleted user?).  I don't know if this is a bug or if there is simply a delay between reputation updating, but I figured it was worth reporting.    Sadly I cannot prove that I had 3,606 reputation yesterday. What would you call someone who makes no lasting impression? It's stated that the gradient of:  $$\frac{1}{2}x^TAx - b^Tx +c$$  is   $$\frac{1}{2}A^Tx + \frac{1}{2}Ax - b$$  How do you grind out this equation? Or specifically, how do you get from $x^TAx$ to $A^Tx + Ax$? What is the use of the yield keyword in Python? What does it do? For example, I'm trying to understand this code1: def _get_child_candidates(self, distance, min_dist, max_dist):     if self._leftchild and distance - max_dist &lt; self._median:         yield self._leftchild     if self._rightchild and distance + max_dist &gt;= self._median:         yield self._rightchild    And this is the caller: result, candidates = [], [self] while candidates:     node = candidates.pop()     distance = node._get_dist(obj)     if distance &lt;= max_dist and distance &gt;= min_dist:         result.extend(node._values)     candidates.extend(node._get_child_candidates(distance, min_dist, max_dist)) return result  What happens when the method _get_child_candidates is called? Is a list returned? A single element? Is it called again? When will subsequent calls stop?   1. This piece of code was written by Jochen Schulz (jrschulz), who made a great Python library for metric spaces. This is the link to the complete source: [Module mspace][1]. I have some conditions for some background job to run:  condition-command &amp;&amp; condition-command &amp;&amp; background-job &amp;   The problem is: I want the conditions to block until the job runs, as if I had run:  condition-command; condition-command; background-job &amp;   But it isn't a condition, if previous command fails I do not want the job to run.  I realised it is asynchronous, but it should not, in my mind the both following scripts should be the same, but they do not:  sleep 2; echo foo &amp; sleep 1; echo bar; wait   # prints foo, then bar: correct sleep 2 &amp;&amp; echo foo &amp; sleep 1; echo bar; wait # prints bar, then foo: bug   I know if I test $? variable it would work, or if I put the last one inside a subshell (but then I would lost job controls, I want to avoid daemons), but I want to know why bash make it this way, where is it documented? Is there any way to prevent this behaviour?  Edit: Chained ifs is disgusting, that is why I will not accept it as a alternative way. Edit 2: I know a subshell is possible, but it will not work for me, let us imagine I want to run a bunch of commands then wait in the end. It will be possible if i check the existence of /proc/$PID directory, but it would be a pain in the neck if there are several jobs. Edit 3: The main question is WHY bash does it, where is it documented? Whether or not it has a solution is a bonus! PostgreSQL check bloating of a table How does one type Chinese in LaTeX? Prove that $T(n) = T(n/3) + T2n/3) + 5n$ is $O(n log n)$