Wirecutter

This heated mat is great for cats who love snuggling against warm things (or people) and elderly cats who need help keeping warm.

TechGearLab

There's a certain type of cat that is constantly seeking out the warmest spot in the house. If your pet falls into this category, we think the K&H Pet Products Thermo-Kitty Mat is one of the most reasonably priced ways to make their life just a bit comfier. This simple mat can easily add a dose of warmth to your kitty's favorite spot, allowing for even more lounging enjoyment. It's also a cheap and easy way to add a bastion of warmth for your pet on those winter days when you're not home and want to turn the heat down. To top it all off, the cover is machine washable, making it easy to keep the bed fresh and clean. 
This bed lacks any sides, meaning it is better suited to cats that like to sprawl as they sleep, or to being added to a spot that your cat already favors. If you're looking for a standalone bed that can entice your cat to sleep in a different area, this bed probably won't cut the mustard. However, it's perfect for making your cat's favorite spot even cozier. 

Heated Cat Bed Comparison