Plug-in solar—small, self-installed systems that connect to a standard outlet—cost 80–97% less than traditional rooftop arrays, and are used widely throughout Europe. In the United States, however, outdated regulations prevent widespread adoption. This white paper explores how plug-in solar could transform energy affordability and resilience for millions of U.S. households, providing case studies, forecasting cost and adoption trends, and detailing necessary regulatory reform.

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In 2025, Utah passed bipartisan, budget-neutral regulatory reforms that exempt systems 1,200 watts or smaller from interconnection rules designed for larger rooftop arrays. If five or more additional states adopt similar reforms, we project the market will experience the following effects:

• Market forces will drive widespread adoption without subsidies, tax credits, or incentives;

• The cost of plug-in solar arrays will fall to ~$0.50/watt within 2 years;

• Average payback periods will fall to ~4 years by 2028, ~3 years by 2032;

• Approximately 24M households – 60M people, or one in six Americans – will use a plug-in solar system by 2035.