Texas trial demonstrates over 50% summer peak demand reduction by residential solar systems


An Austin, TX research trial has demonstrated an average 58% peak demand reduction at homes with residential solar systems, with a range from 54% for homes with south-facing solar systems to 65% for those with west-facing systems.

The trial, reported by Pecan Street Research Institute, was conducted during the last summer from June 1 – August 31, 2013 It involved 50 single-family homes, randomly selected from 175 homes with rooftop solar PV, with roughly half having south-facing solar arrays, a quarter having west-facing arrays, and a quarter a combination of west- and south-facing arrays.

The study considered only the electricity generated by the rooftop solar system that was actually used in the home, and excluded electricity that was sent to the grid.

“Residential solar systems have understandably raised concerns about their impact on electric reliability,” said the report’s lead author, Pecan Street CEO Brewster McCracken. “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 behavior or sacrifice comfort.”

Some other key findings from the study:

  • During peak hours, homes used 80% of the power generated from the rooftop systems and returned 20% to the grid. In the homes with south-facing systems, 78% of the power generated was used in the home and 22% was returned to the grid. In homes with west-facing systems, 84% was used in the home and 16% was returned to the grid.
  • Over the course of the full day, 64% of the energy generated by the rooftop systems was consumed on-site and 36% was returned to the grid.
  • Over the course of the full day, and not including surplus energy returned to the grid, the solar systems provided 36% of the average power used per home. Nearly a third (32%) of the power was generated during peak demand hours.