Digikey will list the power consumption for you. From what I learned there are are a few types: continuous, pulse and intermittent (defined on data sheet below)
Here is a sample showing one series of solenoids, with the different power consumption values for each type. I got some of the continuous duty variety since they are listed at <10 W continuous. Have not had time to test yet.
I wish I had more time to ask a Q&A before ordering because I really only need a pulse type solenoid for what we're doing, but a pulse lists its wattage as well over 10 W as shown
here My curiosity is if the continuous version of the solenoid uses 4W and the pulse version of the same series uses 40W for short periods of time, does it meet R29? My guess was no.
-matto-