The starting point for Vardar AS was the Buskerud County Administration's focus on hydropower development and power transmission, which began in 1919.

The development of a regional power grid was the first area of activity, while the development of hydropower started in the early 1960s with the development of the Mykstufoss power station in Numedal. The first year of operation for this power station was in 1964. From 1970 to 1983 four new power stations were commissioned and two were acquired.

The Energy Act, which entered into force in 1991, was the starting point for a comprehensive restructuring of the energy sector. The operations were organised as a limited company as of 1 January 1991, and later the business areas of grid and power production were converted
into separate limited companies. At the end of the 1990s/beginning of the 2000s, the Municipality of Drammen's investments in the power sector were coordinated with the County Administration. As a result of this process, Vardar AS and the Municipality of Drammen both became 50 per cent owners of Energiselskapet Buskerud (EB). EB changed name to Glitre Energi in 2016.

In addition to indirect ownership of power production via EB, Vardar owns the subsidiary Vardar Vannkraft AS, which controls two-sevenths of the production at the Usta and Nes power stations in Hallingdal. The other owners of these stations include E-CO Vannkraft (E-CO Energi) and Øvre Hallingdal Kraftproduksjon (Akershus Energi). Vardar's ownership interests in hydropower represent a production volume of just under 2,000 GWh annually.

In 2001 Vardar acquired Kvalheim Kraft AS together with Østfold Energi and built the Mehuken I wind farm. Wind power became thus a new focus area for Vardar. Cooperation with Østfold Energi was expanded significantly in 2006 when the partners established the wind power company Zephyr AS in cooperation with Dong Energy, as a driver of project development and management of the wind power plant for the owners. In addition, Vardar established the wholly owned subsidiary Vardar Boreas in 2009, as an ownership vehicle for wind power in Norway. In 2013, this focus area was expanded to include Sweden, through the company Vardar Vind AB.

Through Vardar Eurus, which was established in 2004, the main wind power focus shifted from Norway to Estonia due to a better regulatory framework. The first wind farm in Estonia, OÜ Pakri Tuulepark, was commissioned in 2005. Vardar Eurus now has wind power interests in all of the Baltic States, and it is one of the leading players in Estonia and Lithuania.

Vardar's business concept is to contribute to increasing the supply of clean, renewable energy. As an element of this, Øvre Eiker Fjernvarme AS was established in 2003, and the company's district heating plant in Vestfossen was commissioned that same year and is based on biomass as the main source of energy.
The focus on bioenergy increased significantly through the establishment of Hønefoss Fjernvarme in 2006, and the development and operation of district heating operations in Hønefoss. Hønefoss Fjernvarme changed its name to Vardar Varme AS in 2014, and currently owns all the shares in Øvre Eiker Fjernvarme AS.