A warehouse is compute: it runs queries and you pay for it in credits by the second while it's running, with a 60-second minimum each time it starts. Storage is billed separately.
CREATE WAREHOUSE etl_wh
WAREHOUSE_SIZE = 'SMALL'
AUTO_SUSPEND = 60
AUTO_RESUME = TRUE
INITIALLY_SUSPENDED = TRUE;
Sizes double each step: X-Small uses 1 credit an hour, Small 2, Medium 4, Large 8. AUTO_SUSPEND stops it after that many idle seconds, and AUTO_RESUME starts it when a query arrives. Change settings with ALTER WAREHOUSE ... SET ..., and stop one by hand with ALTER WAREHOUSE ... SUSPEND.
Scale up (a bigger size) when single queries are slow. Scale out (a multi-cluster warehouse, on Enterprise) when many users queue at once. Creating and changing warehouses takes SYSADMIN here.