The Volvo 7900E will run along Route Six, taking passengers from the civic centre via the city centre and on to Cardiff Bay.
A large charging station has been installed next to Alexandra Gardens in Cathays Park, which is expected to power the bus within three to six minutes.
The eight-week trial’s key objective is to prove electric public transport could be viable in the city and in other parts of Wales.
It is being run in collaboration between the Welsh Government, Cardiff Council, Cardiff Bus, Volvo and ABB.
Environment Minister Hannah Blythyn said: “Improving air quality is one of my top priorities. I’m delighted the Welsh Government and Cardiff Council are working with businesses to present innovative solutions to reduce vehicle pollution and improve air quality in our city centres.
“The new buses complement our recent consultation on Clean Air Zones which aim to tackle excess levels of roadside nitrogen dioxide.”