Merry, as pp said, there is a normal hot cold mixer lever on one side, and the other side has a spring loaded safety button for the boiling water.
Mine doesn't need to run through the water - I allow about a second's worth of water to run, then it is boiling water. All visitors (who are likely to be making their own tea) get the hot water safety brief when they come. Mainly consisting of a warning that, yes, it will definitely be boiling, you need to trust it, and never feel the urge to run your hand under it just to check.
BIL had the safety brief, but didn't believe me. One burnt hand later...
I don't find it expensive to run, I think the Franke website says it is about £32 per year. You do need to be aware that there is a filter for the boiling water. They say it should be replaced every 6 months, but we just replaced ours, after 3 years. The flow was starting to get quite slow, but the new filter fixed this. It cost £36 for the filter, and we had to remove the kick board to get at it.
The good thing about having the unit under the cupboard behind the baseboard is that it doesn't take up cupboard space (the unit is about the size of a 1980s VCR), and it has the added benefit of heating the floor below it, giving a nice warm spot to stand on in front of the sink (we have to turf the cats off that spot to get at the sink).