LIPA has raised its rates for the second time in just two months, this time by just over 4 percent.
Add that to a hike in August, and bills have risen by more than 8 percent.
The average customer will pay $6.21 more in September, on top of the $5.71 hike in August.
LIPA blames the double-hike on higher energy costs during the high-demand season.
The utility also moved last Friday to suspend its popular rebate program for home solar-energy systems.
LIPA has 1.1 million customers.
