The preliminary proposal, calling for an increase by 68.49 levs per 1,000 cubic metres, is due to the rise in the international prices of energy resources that are an alternative to natural gas in recent months, Bulgargaz said in a statement.
The company will unveil its final proposal just before submitting it to the country's energy regulator on December 11, the company added.
The price adjustment, made on a quarterly basis, must be approved by the regulator to take effect.
(1 euro =1.95583 Bulgarian levs)