AFAIK they are only available as a 110V version, so to use in the EU or where you have a 220V supply they would need a simple step down autotransformer to use them. Just note that all the autotransformers you find for cheap often are not legal, as they use a socket outlet as both power in and power output, with the pins of the supplied plug being live when plugged in to the mains. Simple enough to take the end cover off on the 220V side and connect it correctly to a lead with a strain relief instead of the plug, you just need to get an old lead with the strain relief cable grip on it and make an appropriate hole and then connect it inside, adding the non existent earth connection it needs to the frame of the transformer. As well look at how the windings are connected, as normally you find the transformer is wound as a 55V, 110V, 55V set of 2 windings. You need to just remember that the output will float at a minimum of 55V above earth. Then you plug the Hakko into the 110V output permanently, and it will work with pretty much no problems. There are issues with the differing mains frequencies, but this will not affect heat output, only slightly increasing copper loss in the internal transformer.
