Clean energy could be among the hardest-hit sectors if the U.S. government does not raise the debt ceiling and then defaults on the national debt.

If there is a default, it could hurt in direct ways, by stopping payments for cash grants and loan guarantees that support many renewables projects. It could also hit innovation, by putting the Department of Energy program for cutting-edge energy technologies, ARPA-E, at risk.

A default could also hit indirectly, by pushing down the value of the U.S. dollar, as well as pushing up interest rates, which would affect financing for renewables projects that require large up-front investment.

Any kind of budget deal will have to include