Once a further five single-deck vehicles are added to the fleet in 2018, it will become the first fully-electric route in the city.
Lothian Buses managing director Richard Hall said his company fully supported the strategies of the Scottish government and City of Edinburgh Council on improving local air quality.
He said: "These buses are not only fitted with zero emission technology, they are also quieter and smoother, offering a better customer experience for the thousands of customers who travel with us every day.
"Electric bus technology is here and we need to embrace it and ensure that it is part of our future fleet and business planning strategies.
"It has a really important and exciting role alongside traditional diesel and hybrid technologies."
Green Bus Fund
The vehicles can run for up to 130 miles, and take three to four hours to fully charge.
When the buses brake, the energy created is recovered back to the battery to be used as power for the engine.
Transport Minister Humza Yousaf said: "This is huge. Lothian is leading the pace with the first fully-electric buses here in Edinburgh."
Money has been made available for similar projects through Transport Scotland's seventh round of the Scottish Green Bus Fund.
On Thursday, £1.4m was awarded to support the purchase of 47 new green buses between four companies.
Scotland's first all-electric buses were launched by Stagecoach in Inverness last year.
Source (BBC): http://www.bbc.co.uk/news/uk-scotland-scotland-business-41429207