Electricity prices for Chilean residents on the central SIC power grid will retroactively decrease an average 0.3% from April, the government's National Energy Commission said Tuesday.

Residential rates are indexed to wholesale electricity prices, or node rates, which are calculated using international fuel prices, local generation costs, the peso's exchange rate against the dollar, water reservoir levels, and utilities' capital expenditures, among other factors.

Chile imports nearly 98% of the fossil fuels it consumes.

For an average home consuming 150 kilowatt hours a month, the electricity bill will decrease to 16,147 Chilean pesos ($33.82), from CLP16,190.

The SIC grid provides power to 90% of Chilean homes from the northern city of Taltal to the southern island of Chiloe.

The main power companies supplying energy to the SIC grid are Empresa Nacional de Electricidad SA (EOC, ENDESA.SN), AES Corp. (AES) through its AES Gener SA (AESGENER.SN) unit, and Colbun SA (COLBUN.SN).

Electricity prices for residents on Chile's northern SING grid, meanwhile, will decline an average 6.2% from April, retroactively.

For an average home consuming 150 kilowatt hours a month, the power bill will fall to CLP16,926 from CLP18,037.

SING provides power to 10% of the country's residential clients and most of the largest copper-mining companies.

Chile's Energy Ministry adjusts wholesale electricity rates every six months, resulting in increases or decreases in the price charged to regulated customers, including residential clients.

Write to Graciela Ibanez at graciela.ibanez@dowjones.com