JFYI: having just used this service i thought it might help someone as so many seem to be planning ot go to Spain this summer.

The "consigna" luggage lockers cost 4,50 euros for the larger one. There is a machine to get the exact change you need. But if it is not working you will not be able to check your luggage without exact change.

There is a smaller locker but i cannot remember the price. Probably one euro less.

This is all located in the Sants train station. The good news is that you are in charge of your key so there will be no delay when you return to collect it by having to wait in lines.. like at rome train station.

also, do not expect for certain to have luggage carts waiting when you disembark your train. Twice there were NONE for the passengers arriving from airport, or going to airport.

It was quite frustrating to think that upon arrival at BCN if i had needed a cart, there was none where the train arrived.

Fortunately i only had a small carry on. Just keep this in mind.

I wish they would allow those wonderful luggage porters we have at airports in the United States. seems it would be a good earning job for someone.

also, the tourist bus does have a stop at Sants train station, so you can actually start your touring as soon as you are off the train and use it to get to your hotel.