Why More Solar Panels Should Be Facing West, Not South | Alternative Energy | Forums

For years, homeowners who bought solar panels were advised to mount them on the roof facing south. That captures the most solar energy over the course of the day, which benefits the homeowner, but does so at hours that are not so helpful for the utility and the grid as a whole.

Mount them to catch the sunlight from the west in the afternoon, and the panels’ production over all would fall, but it would come at hours when the electricity was more valuable.

But that idea is slow to take hold. A new study of 110,000 California houses with rooftop solar systems confirmed that a vast majority of the panels were pointed south because most of the panel owners were paid by the number of kilowatt-hours the panels produced. Pointing them southward maximizes production over all, but peak production comes at midday, not in late afternoon, when it would be more helpful.

In late afternoon, homeowners are more likely to watch TV, turn on the lights or run the dishwasher. Electricity prices are higher at that period of peak demand. “The predominance of south-facing panels may reflect a severe misalignment in energy supply and demand,” said the authors of the study, Barry Fischer and Ben Harack. They work for Opower, a company that provides software that electric companies can use to manage their relationships with their customers.

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