Traditional Japanese wooden houses don't have central heating - instead some rooms have air conditioning (イアコン), the toilet seat is usually heated, while the living room often has a kotatsu heated table (炬燵, こたつ). Modern kotatsu heaters are compact electrical units mounted on the underside of a low table, which is then covered with a quilt hanging down to the floor to trap the heat. Family life in winter is centred on the kotatsu, for watching TV, eating dinner, etc - with everyone sat round the table with their legs and lower body nicely warm.
A kotatsu heater is probably my best souvenir purchase from Japan to date. The heaters are small enough to bring back in a suitcase (unlike a complete kotatsu table unit), maybe even in hand luggage? To create a kotatsu here in Scotland I've attached the heater to an Ikea LACK coffee table, and added a large duvet and voltage transformer:
The kotatsu is a welcome addition to the traditional stone-built Scottish cottage where we live, which is hard to get warm in winter - despite retro-fitted central heating with radiators. If this winter gets really cold, we'll move the kotatsu in front of the open fire place...