The St Bernard is the dog that loves to sleep the most.
St Bernard dogs are very large dogs and they are pretty lazy especially when they are indoors.
A St Bernard may sleep as much as 8 to 10 hours per day and also sleep that much through the night if they are being lazy and are indoors.
Other dog breeds that sleep the most are Bull Dogs, Basset Hounds, Greyhound, Great Danes, Pugs, the Chow dog, Chow Chow, Shih Tzu , French Bull Dog, Labrador Retriever, Pekingese, Chihuahua and the Great Pyrenees.
All those dog breeds sleep quite a bit during the day and during the night.
Most dogs when being lazy will sleep a lot more and when they are inside the house and cooped up in the winter the dog may sleep more as well.