The environmental problem in land activity created a big alarm especially close to very inhabited zones; in the marine field, after a very long period of stand by, the problem is felt mainly in the big water cities where, close to the harbours, a heavy microclimate expose people who live nearby to  risks of serious damages for their health.

As well known, one of the main causes of air pollution in the harbours is the contemporaneous presence of many ships producing large amounts of noxious substances and the shore-side power supply of these ships is doubtless the better solution.

Shore connection (also called “cold ironing ”) means to supply ships at berth in feeding points close to the mooring sites so that the diesel electric generators can be switched off and no exhausts are delivered during ship stay.

A real standard solution for cold ironing is not available yet; actually, the kind of installation depends on the specific environmental and commercial vocation of the port as well as on the kind of ship to be fed.

In this paper, therefore,  the main features of the electrical shore connection together with the technical and economic factors behind any particular project are analyzed.

Particular attention is given on the electrical infrastructures possible, their compatibility with the vessel electrical system and the vessel modifications usually required.

Quantitative assessments  of the main harmful air pollutants avoided (sulphur oxides, nitrogen oxides, etc) using such shore connections are also reported; they are built considering the present marine diesel engines rules for European harbours, even specified in the paper, and aim to show how, even if the rules are correctly applied, there is no guarantee the harbour is a safe place.