“Countries that aggressively expand solar have significantly higher costs than their neighbors” for energy, said Johnson, who has sell ratings on five of the six solar manufacturers he covers.

Solar power doesn’t compete with oil as a source of electricity except on small islands and in some crude exporting countries. Oil generates less than 1 percent of U.S. power supplies and 5 percent globally.

That link may be more emotional than based on fundamentals, said Josh Baribeau, an analyst at Canaccord Genuity Inc. in Boston.

“We believe that part of the solar sell-off may also be driven by the fall in oil prices,” he said in a note to clients on Oct. 14. “We have never liked the psychological correlation between solar stocks and oil, but it exists to some degree.”

All but two companies in the solar index have declined in the past month. Yingli Green Energy Holding Co., the biggest panel maker, slipped 17 percent and Trina Solar Ltd., the No. 2 producer, declined 24 percent. The index rebounded to gain 2 percent at the close yesterday in New York.

“A drop in oil doesn’t affect our space,” David Crane, chief executive officer of NRG Energy Inc., said yesterday in an interview. This year, the largest U.S. independent power producer acquired three solar power supply companies.

Copyright 2014 Bloomberg

Lead image: Oil rig via Shutterstock