Solar panels typically generate electricity at only around 13% of their stated capacity. For windmills, it's around 22%. And those figures vary by month.

Wind and solar companies were already bracing for Congress to end federal subsidies. But the Senate bill goes even further and penalizes those industries.

A Republican plan heading to a vote in the Senate would quickly end incentives for clean energy and impose new taxes on some wind and solar projects, while boosting production of coal used to make ste