The Spirit of Vancouver Island and the Spirit of British Columbia will both be converted to run on diesel and LNG by 2018.
The upgrades, which wlll be part of the normal mid-life span upgrades for the vessels, will also include modifications to the hulls to make them more fuel efficient.
The estimated cost of the conversions was not released by BC Ferries, but they did release an estimate that they will save approximately $9.2 million per year in fuel costs over the remaining 27-year lifespan of the vessels.
Earlier this year BC Ferries announced plans to build three new smaller vessels that would also run on LNG.
CEO Mike Corrigan says the switch to LNG will help keep fares down.
“We are well aware that fare affordability is a concern for our customers and operating on LNG, which is approximately 50 per cent cheaper than marine diesel, is a game changer for BC Ferries,” said Corrigan in a statement released on Monday morning.
The two vessels operate on the busiest route between Swartz Bay and Tsawwassen, and consume more fuel than any other vessels in the fleet. BC Ferries spent $126 million on fuel last fiscal year and the two Spirit-Class vessels consumed approximately 15 per cent of the fleet total.
Further fuel savings will be made by coating the hulls with a low friction coating and modifying the dated bow and stern designs from to further reduce drag.
The Spirit Class vessels were launched in 1993 and 1994, and have the capacity to carry 410 cars and 34 semi-trucks each.