Geographic monopolies might seem to constitute a major obstacle to exchanges of electricity in Europe. Opening the access to grids is sometimes considered as the solution. But if the aim is to improve the overall efficiency of the European electric system, is open access a good answer? The paper argues that, in vertically integrated industries, the advantages of open access could be offset by the difficulties of marrying competition with the obligation to supply, and by the drawbacks of the new and very complex regulation that it will be necessary to implement.