Independent research house Morningstar has valued state-owned Genesis Energy at around $1.69 billion to $1.89 billion in total, or about $3.25 to $3.50 a share.

At that price, the sale would be worth about $845 million to $945 million to the Government, assuming it sells the maximum 49 per cent.

An analyst report released last week by brokers UBS put the full equity value of Genesis in a range of $1.559 billion to $1.886 billion. The Government said the Genesis share offer will proceed in March, for an April listing, but that it may sell less than 49 per cent if there is not enough demand.

Finance Minister Bill English has gone for an unusual front end book-build process for the share sale, which will be open to both institutions and the broader broking community. On top of its 30 per cent ownership of the lucrative but diminishing Kupe field, Genesis has Tekapo A and B hydro stations in the South Island and the Huntly coal and gas station. It also has the biggest customer base of the generator/retailers.