Terra Firma said it will retain flexibility on the size of the stake to be sold but the firm indicated that it expects to float at least 30% of the company.
The offering is expected to raise up to £1 billion for the British wind power firm.
Over the last three years, group EBITDA has increased from £100 million in 2011 to £125 million in March 2013. Turnover saw a 19% rise over the same period.
The company said it is targeting a £55 million dividend in its first year.