Left-luggage lockers in Granada:
Granada City Center Luggage Storage:
Very convenient place near the cathedral. Leave your bags for hours or days.
There are discounts for advanced booking
Click here
Ilocker:
There is a left luggage place in Plaza Nueva
https://www.granadamap.com/ilocker/index.htm
Bus station
There are lockers at Granada bus station.
Estacion de autobuses.
Estacion de autobuses
To get to the bus station get on a 33 bus from the Gran Via and Avenida de la ConstituciĆ³n
Alhambra
Also there are lockers at the Alhambra. It is free if you have bought a ticket. The luggage office is located outside and downstairs from the main ticket office..
There is some more information here
https://granadainfo.com/alhambra/lockers.htm