Why is this solenoid valve consuming so much power?
The product description is simply wrong regarding power rating, as You can read on the comments from another user:


  "The consideration is the fact that they draw 1.5A continuous while open so you need an appropriate power source and they are dissipating 18W or so of heat. They might overheat with no cool liquid passing through them but can't say for certain"


You can easily measure the solenoid resistance and calculate total power.