The first two zero-emission hydrogen buses will enter service on route RV1 on Saturday 19 December.
Deputy Mayor of London Kit Malthouse unveiled the new buses on Friday and inaugurated the new refuelling plant at First's Lea Interchange bus garage at Leyton.
By the end of 2011 the RV1, which links Covent Garden and Tower Gateway via the South Bank and Bankside, will become the UK's first zero-emission bus route.
The new buses produce no emissions other than water vapour, although the production and transportation of the hydrogen still has a significant carbon impact.
The buses will form the only hydrogen bus fleet in the UK and the largest currently in Europe.
Hydrogen buses are already familiar to RV1 passengers – between 2004 and 2007 three hydrogen fuel cell buses were trialled on the route.
It is a year since the Olympic Delivery Authority granted planning permission for the permanent hydrogen refuelling facility at Temple Mills Lane, Leyton.
The first of the new buses has been undergoing testing since it arrived in the UK in May.
The vehicles were built by Wrightbus in Northern Ireland and then transported via ship to California where the engines were installed.
"This bus will help to solve two of the problems that plague the city: air quality and noise," said Kit Malthouse, Deputy Mayor for policing and Chair of the London Hydrogen Partnership.
"A bus that is both quiet and clean will make a massive difference."
He added: "The one thing we know about Londoners is that they like to kick the tyres. They believe it when they see it.
"In the past there's been an awful lot of talk about hydrogen and not a lot on the ground.
"Well, from next year they will have an entire bus route where not only can they travel frequently and reliably, but they will also be able to breathe easily while they do it – and if they carry a glass, have a drink out of the tail pipe.
"The great miracle of this technology is that this bus produces nothing other than water."
The buses are jointly funded by Transport for London the Department of Energy and Climate Change and the European Union via the Clean Hydrogen in Cities (CHIC) project.