A fund manager, who requested anonymity, said there had been a change of heart over Genesis, which was earlier seen as less attractive than the other power generators put up for partial sale by the Government.
"The broker pool is still open but if you ring up a broker now he will tell you it's too late," the fund manager said.
"On the institutional side, there are some pretty unhappy people," he said. "Clearly people were keen to get access to this issue."
Broking sources said the Labour-Green plan to do away with the wholesale electricity market had become less of a concern than was the case with Meridian and Mighty River Power as the National-led Government continued to poll strongly before September's general election.
Genesis is also offering a high implied dividend yield of 10.8 per cent to 13.2 per cent for 2014, plus a bonus share component.
"Also if you look at the portfolio, it's the most flexible of all the generators to deal with potential changes in the generation industry, so if you have another dry period, Genesis is in the box seat," the fund manager said.
This week five independent reports put a higher value on the company's shares than the $1.55 price tag attached to the power generator and retailer by the Government, but analysts differed on the merits of the asset that sets the company apart from its peers - the Kupe oil and gas field.
Broking house Craigs Investment Partners valued the company, set to list on the NZX on April 17, at $1.35 to $1.65, or $1.63 relative to its peers if it were floated on the market now.
Wellington-based investment firm Woodward Partners valued Genesis at $1.66 to $1.93, with a $1.75 mid-point, while international technology research company Edison valued it at $1.75 to $1.93, with a $1.88 mid-point.
International research house Morningstar put the company's value at $1.60 and Australian equities research group Fat Prophets valued the stock at $1.75.
Genesis has substantial hydro and thermal power generation assets and receives a 31 per cent share of all Kupe's oil, natural gas and LPG production.
The gas component helps Genesis Energy support a high dividend payout and fuels the company's 400MW gas turbine at its Huntly power station.