Installers typically orient solar panels so they face south. But west-facing solar arrays would be more effective at reducing the strain on electric utilities on hot summer afternoons, Texas-based researchers said.
A report from the Pecan Street Research Institute headquartered at the University of Texas at Austin, focused on a small sample of houses in Austin, 24 of them with south-facing photovoltaic panels, 14 with west-facing panels and another 14 with arrays that faced both west and south.
Researchers were surprised to find that west-facing panels produced more power than south-facing panels during the study period, June 1 to Aug. 31, 2013. “During summer peak demand hours (3-7 pm), the gap was even more pronounced: west-facing systems produced 49% more electricity during those hours than did south-facing systems,” the Institute said in a news release.
West-facing solar panels reduced the peak electricity demand from the grid during those hours by 65% while south-facing panels reduced peak demand by 54%, according to the report.
“These findings suggest that rooftop solar systems can produce large summer peak reductions that benefit utilities and customers alike without requiring customers to change their behaviors or sacrifice comfort,” lead author and Pecan Street CEO Brewster McCracken said.
But overall, south-facing panels make more power
Before you get up on your roof and start moving panels around, remember that south-facing solar arrays make more power overall.
Writing at Forbes, Tom Konrad took other bloggers to task for misinterpreting the study and implying, inaccurately, that west-facing panels will out perform south-facing panels all year round.
“The study (which I obtained from Pecan Street) specifically says, ‘Over the course of a full year, a south-facing orientation produces more total energy than other orientations,’” he wrote. “In addition, Brewster McCracken, the president and CEO of Pecan Street, told me that he did not expect that the finding that the west-facing arrays produced more energy even during that three-month period was statistically significant, given the small sample size.”
More arrays should be pointed west, Konrad said, not because they generate more electricity but because “the power they produce is more valuable.”
Some Austin-area utilities, McCracken told Konrad, don’t offer incentives for west-facing solar panels on the grounds they don’t produce enough energy.
“Those utilities are just as confused as the media lemmings who think you get more energy by pointing solar panels west,” Konrad writes.
The report suggests utilities should not only extend solar rebates for west-facing systems but “even offer higher rebate levels than is provided to south-facing systems.”