We all know that Border Collies have a need for speed and Basset Hounds have a need for naps, but where do Goldendoodles fall in that spectrum? The straight forward answer is… it depends.
Temperament (of both pup and parents)
This is probably the biggest factor. Even more so than what breed the dog is. As crazy as it sounds, you can have an Australian Shepherd that has less energy than a Golden Retriever.
To put this into practical terms, if you are looking for a low energy dog that will need very little exercise, look at both of the parents of the pup and see if they have that same temperament that you are looking for. Next, (assuming you are picking a puppy from a litter) you will look for the lowest energy puppy from the litter between those two parents who you liked.
The same goes if you are looking for an active dog to go running marathons with. Find parents that have that temperament, then from the litter pick the highest energy pup.
Doodles Size
It has been my experience that the larger the dog, the more mellow and lower energy they are. So if you are wanting a couch potato, you might do yourself some good by looking for a larger Goldendoodle.
Summary
All of that is to say, on average, Goldendoodles require moderate exercise, a walk or two a day should be plenty to satisfy the average Goldendoodle. If you have a backyard with room for them to play they very well could get all the exercise they need right out there, and if you have two Doodles, they will wear each other out playing which is always good for you.