Patrick Martin, 37, who had been living in Tooting, south-west London, had his sentence reduced to 28 years after the Court of Appeal concluded that allowance should be made for the fact that "death and injury was not the primary object" of the bombing campaign.
Martin was one of six members of a Provisional IRA active-service unit jailed at the Old Bailey in July 1997, who were described by the trial judge Mr Justice Scott Baker as "out to destabilise the community by wrecking electricity supplies to the South-east of England".
From early June 1996 the terrorists intended to cause the biggest blackout since the Blitz of the Second World War, but were thwarted by a sophisticated undercover operation by police and MI5 officers.
Imposing 35-year sentences on each of the terrorists, the trial judge told them: "You were reckless as to the number of people who might be killed or maimed as a consequence of your planned bombings."
Yesterday Lord Bingham, the Lord Chief Justice, sitting with Mr Justice Tucker and Mr Justice Richards, allowed Martin's appeal against the sentence, saying: "We have no doubt that the judge in this case was fully entitled to take the view that it called for a sentence of the utmost severity.
"The political, economic and social threat presented by this conspiracy was, perhaps, as great as in any of the cases we have considered.
"We do, however, conclude that some weight must be given to the fact that death and injury, although a likely by-product of implementation of the conspirators' plan, was not its primary object."
The 35-year sentence in reality represented the sort of term served by someone who committed a murder "with severely aggravating features".
The judge said the appeal would be allowed, the original sentence quashed and replaced by one of 28 years.Reuse content