A self-heating bed makes an odd promise, and it is worth being clear about it before you buy: there is no plug, no battery and nothing in it that generates warmth. What it does is refuse to let heat leave.

The pad has a thermal layer built into it that reflects an animal's own body heat back at them instead of letting it sink into the floor, and over the cover goes a lamb fleece style fabric. That cover comes off and goes in the machine, which is the part that decides whether a pet bed lasts a winter or a fortnight. This is the small pad and it measures 48x36cm; Ancol make the pad in three sizes, and it will sit in a crate, on the floor or on the chair you are trying to keep fur off. It arrives in a cardboard wrap rather than plastic.

• Small pad, 48x36cm
• Heat-reflecting core with a lamb fleece style cover
• Cover is removable and machine washable
• No power supply, batteries or heating element
• Works in a crate, on the floor or on a chair
• Supplied in a cardboard wrap

The thing a self-heating pad cannot do. It cannot warm an empty bed, and it cannot tempt a cold animal onto it — the warmth only exists once they are lying there and staying put. If you have a dog that never settles in one spot, or you want something warm waiting for an arthritic old cat before she gets there, this is the wrong product and a heated bed is the right one. Ancol do not publish what the reflective core is made of or how thick the pad is.

Who it's for: owners of a cat or small dog who already has a favourite spot and lies in it for hours — thin-coated breeds, older animals, and anyone who wants extra warmth in a crate without running a cable to it.