INNOGY, the company behind NPower, saw its market value rise by £ 132 as it was closer to agreeing to a 3bn cash offer from German utility RWE.
It is expected to be officially announced later this week.
Innogy of quotes for 257 3/4 pence rise the 11 3/4 Pence still lower than expected of 273 pence.
Investors are not sure whether the two will complete the deal.
Not only have the negotiations been protracted, but some are concerned that the current bid may not win the support of major shareholders of Innogy.
With more than 6 Jing Shun.
5%, said the value of Innogy is close to 300 p.
Neil Woodford, fund manager, said the current offer could underestimate Innogy's Regenesys battery --
Storage business.
But he will not make up his mind until he sees the firm offer.
Another big investor said a proposal from the board would block bids, especially if there were no other buyers.
He believes that Innogy, which was stripped out of the old national power generation business 19 months ago, will fall to 220 p if the transaction fails.