Falkirk firm Alexander Dennis has won an order for 47 of its green buses.
Stagecoach is paying £9m for vehicles powered by diesel and electricity, with £4m support funding from Whitehall.
The deal aims is to cut emissions by 30% on routes in Newcastle and Sheffield.
Part of the energy-saving design is to charge the batteries through power released when braking, in technology developed with BAE Systems.
The Falkirk company is building 100 of the Enviro-buses this year, and plans for 150 next year.
It has 56 of them operating with Stagecoach in Manchester and Oxford, with 40 in London and the Thames Valley. Five have been ordered by SPT in Strathclyde.
They cost about 30% more than equivalent diesel buses. That is why the UK and Scottish governments have set up funds with which to subsidise bus operators to buy lower-emission fleets.
Alexander Dennis employs 960 people at its Falkirk works and 1,100 in other parts of Britain.
Les Warneford, managing director of Stagecoach UK Bus, said: "Buses and coaches already deliver a major carbon saving over using the car, but new technology is only part of the answer to the challenge of climate change.
"We also need better bus priority, improved bus speeds in our cities and investment in park and ride if we are to maximise the potential of buses and coaches and make it more attractive for people to switch to public transport."