Marlene Holzner, the European Commission’s energy spokeswoman, said: “The commission believes that careful attention must be paid to ensure that measures employed to eliminate the tariff deficit do not negatively affect the investment climate in Spain’s energy sector. In particular, ensuring a good climate for investment in renewable energy is a matter not only for Spain but for the European Union as a whole.”

The July decree, which has been rubber-stamped by the Spanish Parliament, laid out a framework for a thorough overhaul of electricity-sector regulations — to be completed by the end of the year with the publication by the government of detailed new rules.

The overall goal of ending the tariff deficit has broad support, including from the renewable energy industry, but nobody is happy with how the government has proposed to split the unavoidable economic pain.

Renewable energy, which for years was nourished and pampered — making Spain a global leader in the field — will bear by far the brunt of the reforms, both the government and industry experts said. In particular, proposals that would result in retroactive subsidy cuts have deeply rattled the sector.

The proposals have the potential to deliver long-term regulatory stability in the sector, said Tania Tsoneva, a credit analyst with Standard & Poor’s. “At this stage, however, it is still too early to conclude whether the reforms can and will be implemented,” she said.

The problem “essentially reflects a political unwillingness to pass all costs onto final customers,” said David Robinson, an economist in Madrid who specializes in energy policy and who is a senior research fellow in the Oxford Institute for Energy Studies.

“The regulatory system for renewables was badly designed and very expensive,” he said. But the proposed solution risks making some problems worse, he warned.