I finally bought heated water bowls at TSC for $20 each, and my oldest son found these nifty indoor-outdoor halogen light fixtures for $10.77 each at Lowes and installed them on the lids of the boxes for me. There's a tiny gap for the cord to come out, but the lids all have an overhang so rain still doesn't get in. The mounting screws don't go all the way thru the lids, either.
Any light fixture could be used, but the beauty of these is that they are a heavy metal canister and self-contained -- the dogs can't get to the bulb. They put out a fair amount of heat. I will have to shut them off of a daytime until really cold weather sets in.
When it's time to change the bulb, just lift the box lid and the lamp is facing you. Unscrew the front off the fixture, pop in the new bulb, screw the cover back on. The bulbs are about $5 each. You can't touch them with your hands so use a piece of cloth or gloves to handle them. If one were worried about the dogs sleeping with light, I suppose you could paint the glass cover black.
He also installed an air curtain out of material he already had to keep drafts out, and hold in the heat a bit. The dogs were toasty last night and their water doesn't freeze, so I am a happy camper and ready for the winter with a total dollar investment of $35 per kennel! (not including cords)

Grandson Sam helped.


I need a better way to protect the cords for the winter weather.

I actually have rubber stall mats under the kennels like the pic below, but they kick the cedar out of their boxes.

All of it would look better if I kept the grass cut and those boxes washed out better. I can't believe how dirty they get the white walls of the boxes!