I use a
heated dog bowl connected to an extension cord in the covered area that they eat their feed in. I also use a couple big
2 gal rubber bowls near places they like to lay that I have to fill up/break the ice for daily when it's below freezing. You can also use a bucket de-icer in your dog bowl like
this or you can get a heated chicken waterer that you can use all year round like
this one. There's more options out there and maybe better ones, those are just some of the ones I use or have considered.