Powering down is the objective of the eighth annual Earth Hour Saturday night.
The global event promotes energy conservation, and working together to tackle climate change.
Sarnia is one of 500 Canadian municipalities taking part.
Bluewater Power President and CEO Janice McMichael Dennis there has been little impact locally over the last couple of years, mostly due to daily conservation efforts by customers.
Sarnia's first year participating in 2008, there was a 3.5 percent reduction in power.
Earth Hour runs from 8:30pm until 9:30pm.