When you leave a Pokémon at a Power Spot, it stays there to assist future Trainers after you win a Max Battle. The stationed Pokémon can earn Candy, increase the attack bonus for players fighting that Power Spot Boss and contribute to the chance of special wild encounters around the Power Spot.

What happens when you leave a Pokémon at a Power Spot?
Pokémon GO offers the option to station a Pokémon there after a successful Max Battle. You choose one of the Max Pokémon from your battle party and station it at that location. It remains your Pokémon; you are not transferring it, trading it or permanently giving it to the Power Spot.
The purpose is cooperative. As more Max Pokémon are stationed, future Trainers challenging the same Power Spot Boss can receive a stronger attack bonus. A busy Power Spot with several stationed Pokémon can therefore become easier for the next group.
What rewards do you get when you leave a Pokémon at a Power Spot?
The main personal reward when you leave a Pokémon at a Power Spot is Candy earned as the Pokémon assists at that Power Spot. Pokémon GO shows the Pokémon’s Power Spot status and progress while it is stationed. Event bonuses can temporarily improve these rewards, so the exact amount shown in game is more reliable than assuming every event uses the same cap.
Rewards are delivered when the Pokémon returns. That can happen automatically after it has assisted enough, when the Power Spot closes, or when you manually recall it. Power Spots are temporary, so a stationed Pokémon is not locked away forever.
Does a Pokémon help other players when you leave a Pokémon at a Power Spot?
Yes. Helping other Trainers is the biggest system benefit when you leave a Pokémon at a Power Spot. The more Max Pokémon stationed at the Power Spot, the larger the attack bonus can become for Trainers taking on the boss. More stationed Pokémon can also increase the chance of a wild encounter appearing around that Power Spot.
How long does it stay when you leave a Pokémon at a Power Spot?
You do not choose a fixed number of hours when you leave a Pokémon at a Power Spot. It remains stationed until the game returns it because it has assisted enough, the Power Spot closes, or you recall it yourself. The Today View shows how long your stationed Pokémon have been away.
Can you use a Pokémon after you leave a Pokémon at a Power Spot?
While you leave a Pokémon at a Power Spot, it is stationed rather than sitting freely in your normal active roster. If you need that specific Pokémon for another battle, open Today View, select the Pokémon under Pokémon at Power Spots and recall it. Once returned, you can use it normally again.
Can your Pokémon be defeated or lost?
No. Other Trainers are not attacking your stationed Pokémon the way opposing teams attack a Gym defender. It assists their Max Battles. Even if the Power Spot disappears, the Pokémon is returned to you rather than being deleted or abandoned at the old map location.
When should you leave a Pokémon at a Power Spot?
It makes sense to leave a Pokémon at a Power Spot when you have another usable Max Pokémon for your own battles and the species offers Candy you still need. Rare Max Pokémon can be particularly appealing because ordinary catches of that species may be limited.
It may be better to skip stationing your only strong counter if you plan to chain several difficult Max Battles. You can always station a different member of the team or recall a Pokémon later if your plans change.
Is it worth it to leave a Pokémon at a Power Spot?
Usually, yes, if doing so does not remove a Pokémon you immediately need. When you leave a Pokémon at a Power Spot, you contribute to the local Power Spot, can earn Candy and may help improve nearby wild encounters. There is no permanent sacrifice involved, and you retain the ability to recall the Pokémon from Today View.
The practical approach is to leave a Pokémon at a Power Spot when the reward species matters to you, then keep an eye on its progress. If you need it back or the useful rewards have already been earned, recall it and move on to the next Power Spot.
For current game updates, feature changes and official announcements, check the official Pokémon GO website.
