With Norway's abundance of hydroelectricity and the high cost of importing coal to run the steam locomotives, there was considerable economic benefit to be realised by electrifying the line.
Plans for the electrification of the line had existed since the line was opened.
In 1912 the line from Nesttun to Bergen was proposed electrified and rebuilt to double track, following the opening of the electrified Thamshavn Line in 1908.
During the planning of the Hardanger Line and the Flåm Line during the 1930s it was again proposed to electrify the line.
However, although both the branch lines were built with electric traction, the main line was not.
Counter-suggestions were raised proposing a conversion to the locomotives running on oil or coal dust.
In 1939 a plan for national electrification was launched, and the Voss Line was top priority.
But the breakout of World War II set the plans back, and not until the 1950s was it again possible to afford such investments.
Vossebanen took electric traction into use on 2 July 1954.
The electricity is supplied via an overhead line.

In 1952 a new plan was launched by parliament to electrify 1,153 kilometres (716 mi) of railway, with the line from Voss to Hønefoss prioritized fourth.
The following year NSB launched the "away with the steam"-campaign, that would replace all steam locomotives with electric or diesel traction.
Since electrification was not imminent, NSB introduced diesel traction on the Bergen Line in 1958, predominantly using Di 3 stock.
Travel time between the two termini was reduced by about one hour.
During summer the Class 66 diesel multiple units were put into service, but they were not heavy enough to cope with winter and thus only served during the summer months.
The line was electrified in four stages, from Roa to Hønefoss on 1 February 1961, from Hønefoss to Ål on 1 December 1962, from Ål to Ustaoset on 15 December 1963 and finally from Ustaoset to Voss on 7 December 1964.
As the point of electrification moved across the mountain, so did the point NSB changed locomotive on the train.
The new locomotive El 13 was put into service on the electric parts.
The electrification cost NOK 143 million.

The express trains have as one of the main lines always been allocated the newest locomotives by NSB.
When the El 14 was delivered in 1968, it was put into service on Bergensbanen, as was the El 16 in 1977, the El 17 in 1981, and finally the El 18 in 1996.
The older locomotives have been relegated to freight service.
In 2000 electric multiple units were put into service with the Class 73 tilting trains, branded as Signatur and capable of 210 kilometres per hour (130 mph).
However, they cannot be used at those speeds on any part of the Bergen Line, and only some parts of the Asker Line and around Finse can they operate quicker than the other rollingstock used.
There has also been reason to doubt their winter capability on the very demanding Bergen Line.
Occasionally they have been stuck in the snow, and on February 21, 2007 a multiple unit derailed after running into a pack of snow.
As refurbished carriages become available, the multiple units will be removed from the line, and replaced by traditional locomotive-hauled trains.
With Norway's abundance of hydroelectricity and the high cost of importing coal to run the steam locomotives, there was considerable economic benefit to be realised by electrifying the line. Plans for the electrification of the line had existed since the line was opened. In 1912 the line from Nesttun to Bergen was proposed electrified and rebuilt to double track, following the opening of the electrified Thamshavn Line in 1908. During the planning of the Hardanger Line and the Flåm Line during the 1930s it was again proposed to electrify the line. However, although both the branch lines were built with electric traction, the main line was not. Counter-suggestions were raised proposing a conversion to the locomotives running on oil or coal dust. In 1939 a plan for national electrification was launched, and the Voss Line was top priority. But the breakout of World War II set the plans back, and not until the 1950s was it again possible to afford such investments. Vossebanen took electric traction into use on 2 July 1954. The electricity is supplied via an overhead line.
In 1952 a new plan was launched by parliament to electrify 1,153 kilometres (716 mi) of railway, with the line from Voss to Hønefoss prioritized fourth. The following year NSB launched the "away with the steam"-campaign, that would replace all steam locomotives with electric or diesel traction. Since electrification was not imminent, NSB introduced diesel traction on the Bergen Line in 1958, predominantly using Di 3 stock. Travel time between the two termini was reduced by about one hour. During summer the Class 66 diesel multiple units were put into service, but they were not heavy enough to cope with winter and thus only served during the summer months. The line was electrified in four stages, from Roa to Hønefoss on 1 February 1961, from Hønefoss to Ål on 1 December 1962, from Ål to Ustaoset on 15 December 1963 and finally from Ustaoset to Voss on 7 December 1964. As the point of electrification moved across the mountain, so did the point NSB changed locomotive on the train. The new locomotive El 13 was put into service on the electric parts. The electrification cost NOK 143 million.
The express trains have as one of the main lines always been allocated the newest locomotives by NSB. When the El 14 was delivered in 1968, it was put into service on Bergensbanen, as was the El 16 in 1977, the El 17 in 1981, and finally the El 18 in 1996. The older locomotives have been relegated to freight service. In 2000 electric multiple units were put into service with the Class 73 tilting trains, branded as Signatur and capable of 210 kilometres per hour (130 mph). However, they cannot be used at those speeds on any part of the Bergen Line, and only some parts of the Asker Line and around Finse can they operate quicker than the other rollingstock used. There has also been reason to doubt their winter capability on the very demanding Bergen Line. Occasionally they have been stuck in the snow, and on February 21, 2007 a multiple unit derailed after running into a pack of snow. As refurbished carriages become available, the multiple units will be removed from the line, and replaced by traditional locomotive-hauled trains.
Bergen Line