My dog is one and a half and all off a sudden started chewing everything including the kitchen units, I don't know how to stop him.

This is from dogproblemsolutions.com and is very sensible advice:

One great piece of advice to stop your dog from chewing furniture is to re-direct your dog's chewing. As you find your dog chewing on your furniture, you should take a toy and re-direct his or her attention on the toy. When they turn their attention away from the furniture, you need to praise them greatly and give them the toy to continue chewing. Soon your dog will learn to enjoy the praise from chewing appropriately.

To add to Ticks answer try spraying some bitter sprays (available at pet stores) on things you don't want chewed to accompany the toys.

Bitter EX works awesome. You can get it at the pet stores Like Shazamataz said, or Wal Mart. Any thing with Bitter ex works. My mom said they use it in Lysol and some cleaning products so children won't drink it. I know my vet said if I wiped my electrical cords with lysol, the cats would stop chewing them. They won't get enugh to poison themselves just one small taste of that nasty stuff is all they need! Plus it took my mind off them getting electricuted! :P