The landmark €4.5bn ($6.5bn) flotation of Spanish wind power company Iberdrola Renovables has disappointed on its first day of trading in a week when a requirement that US utilities generate more of their electricity from wind and solar power was dropped from an energy bill in the US Senate.

Shares in the wind farm operator, previously a subsidiary of Spanish utility Iberdrola, fell 6% from its €5.30 opening price to a low of €4.97 this morning before recovering to €5.15 at 12.00 GMT.