You can also look up the rated idle power in the datasheets to know beforehand. Anything over ~5w needs cooling and usually they are 10+w (at least the ten or so I have here at home). Some of my disks have a low power more (still 7w) which you can enable with vendor tooling or the correct sas command but ymmv. Check the datasheet, it almost always states max 45c ambient and continuous airflow required.