We bought an electric dog bowl at walmart to use in the winter and it worked great last year. We did quit having the water inside during the warmer months though, because the waterer we had leaked and it was a mess. We fortified the run so we could leave the pop door open all night so they can...
We keep the water inside because sometimes it's 9 am before dh sets them free (usually only on sundays). We keep the food inside because our run isn't totally covered so rain could get in it (from the sides, if we get sideways rain like we did last night).