In the constant juggling act that is the Northwest power grid, utility managers always watch two basic factors: energy supply and energy demand. The two must be equal at all times.Sounds simple, right?Not quite. This year, local and regional utilities have gone to extreme measures to keep things in balance.“We’ve had a tremendous amount of supply mixed with low demand,” said Mike Hansen, a Bonneville Power Administration spokesman.The unusually unbalanced conditions have dropped market energy prices far below normal levels, according to Hansen — a trend that’s continued into this summer. That prompted Clark Public Utilities to shut down its River Road power Generating Plant for an unprecedented period of nearly seven months, said power manager Lynn Latendresse. Basically, it was cheaper for Clark Public Utilities to purchase power from outside the system than produce the energy itself, she said.It’s not unusual for Clark Public Utilities to shut down the River Road facility at times throughout the year. But it has never done so as early as January, and never for this long, Latendresse said. River Road just came back online Aug. 1, she said.“This year has been highly unusual,” Latendresse said.The net impact for ratepayers is essentially a wash, according to Latendresse. Lower energy prices push Clark Public Utilities’ costs down, but they also push down revenues from the electricity it sells to other systems, she said.High water on the Columbia River has provided abundant fuel for the region’s hydroelectric dams since last winter. Meanwhile, an ever-growing collection of wind farms — mostly in the Columbia River Gorge — continue to pump more energy into the system when they’re spinning. The region’s wind farms are now capable of producing more than 3,500 megawatts of energy combined, almost double their capacity just two years ago.