The typical residential electricity bill on Maui will rise by $6.60 a month starting June 1 under an interim rate hike announced today by Maui Electric Co.

The Public Utilities Commission approved the interim agreement on Monday, which allows MECO to raise rates on Maui, Molokai and Lanai by an average of 3.2 percent, or $13.1 million.

The increase reflects a previously owned agreement between MECO and the state Division of Consumer Advocacy. The PUC will continue to review details of the interim agreement and issue a final decision at a later date. If the PUC ultimately approves a smaller increase the difference will be refunded to customers with interest, according to MECO.

The interim increase comes less than three weeks after the PUC gave final approval to MECO for a 1.5 percent rate hike that the company first sought in 2010.

The amount of the interim rate hike will vary by island and electricity use. Residential customers on Maui using 600 kilowatt hours a month will see their bill rise by $6.60 to $242.23. The bill for Molokai residential customers using 400 kilowatt hours a month will rise by $5.25 to $193.21. On Lanai, the typical bill for a household using 400 kilowatt hours a month will go up by $5.56  to $195.79.

The latest rate hike will be used to help cover the operations and maintenance costs, including energy storage projects that will allow MECO to integrate higher levels of renewable energy into its grid, according to the utility. Those projects include a battery system at MECO’s Wailea Substation and an energy storage system on a distribution circuit in central Maui.