On average, dogs spend about 12-to-14 hours of the 24-hour cycle sleeping. Older dogs need significant amounts of sleep simply because, as they age, living becomes more difficult. They tire out more easily and need rest in order to function properly. Puppies , like babies, spend a lot of time exhausting energy while playing and exploring their new surroundings. Because of this, they might need as much as 18-to-20 hours of sleep to recoup! And of course, all dogs need sleep, but it tends to be the bigger breeds that are known for constant dozing.