Soldering irons, a simple iron and a temperature-controlled one, need different wattages while working.
A 30-watt simple soldering iron is okay for modest electronics. Soldering ordinary through hole electronic components and thin wire, even the thin metal legs on direct current power plugs and sockets, should be fine.
While a temperature-controlled soldering iron needs much higher power than a simple iron, for example 80W or more. This allows it to maintain a relatively constant soldering temperature even it is being used at the same time, and heat parts with larger thermal conduction or capacity. It won't slow down an operator, and is a bit more flexible on what it can be used for than a simple iron. That is very important on a production line, or where a lot of soldering joints need to be made relatively rapidly. However, a simple iron is likely to drop too far below adequate soldering temperature, and slow the operator down which will cause boss much loss.