South Korea will cut power usage in the public and private sectors from Tuesday until the end of August as the country faces its worst-ever electricity shortage this summer, the Ministry of Trade, Industry and Energy said on Monday.

Public organizations must cut power use by at least 15% in July and August compared with levels from a year ago and keep temperatures above 28 degrees Celsius, the ministry said in a statement.

Temperatures in large buildings must be kept above 26° Celsius during peak demand.

Private companies and city shops that leave their doors open while using air conditioning will face fines of up to 3 million won ($2,660) from July 1, it said.

The limits on power use follow the closing of two nuclear reactors last month for safety violations.