The U.S. House of Representatives is expected to vote on Friday on climate change legislation that is a high priority of President Barack Obama and Democratic leaders in Congress.

If it passes the House, attention would shift to the Senate, where the environmental bill faces tough opposition. It is unclear how much progress the Senate would make this year on a bill.

Here are main details of the House legislation, which has undergone changes since being approved by the House Energy and Commerce Committee in late May:

* There have been plenty of numbers thrown around on how much the legislation will cost consumers. Republican opponents have claimed $3,100 or more per household annually in higher prices for energy and other goods. Conversely, some supporters have said it will save consumers money as energy efficiencies are achieved. The nonpartisan Congressional Budget Office estimated an average cost of $175 annually for households. It said the poor would enjoy a $40-a-year benefit from rebates and other aid.

* New protections for agriculture are being included to win the support of farm-state lawmakers. Among them: Department of Agriculture oversight of carbon-reduction efforts by farmers, instead of the Environmental Protection Agency; obstacles to corn-based ethanol that EPA had proposed would be put off for at least five years and probably longer; some rural electric utilities would get free pollution permits from the government.

* Many coal-fired utilities would enjoy exemptions on carbon emission reductions for new plants being planned for construction. Environmental groups complain this will seriously weaken the pollution-reduction goals of the bill.

* U.S. emissions of carbon dioxide and other greenhouse gases would be reduced 17 percent by 2020 from 2005 levels. That is less ambitious than the 20 percent initially sought, but slightly more aggressive than the approximately 15 percent Obama proposed.

The legislation sets further pollution reduction goals -- 42 percent by 2030 and 83 percent by 2050, with the latter just slightly higher than Obama suggested.

* About 85 percent of pollution permits under the program would be given out, and around 15 percent would be sold. Local electric distribution companies would get 30 percent of all permits for free and would have to protect consumers from electricity price increases.

Other recipients of free permits: 15 percent to cement, steel, glass and other big energy-using industries; 9 percent to local natural gas distribution companies; 3 percent for companies making electric and advanced technology vehicles and 2 percent for oil refiners.

The free permits are designed to ease industry's burden and prevent large energy price increases for consumers. In 2026, many of the free permits would begin switching to those that must be purchased. Obama wanted all of the permits to be sold, but has indicated flexibility.

* Under cap and trade, fewer and fewer pollution permits would be available to companies over the next several decades. Also, companies that pollute less than their limit could sell some of their permits to others struggling to meet environmental requirements.

* Utilities would have to generate 15 percent of their electricity from renewable sources such as wind or solar power and show a 5 percent gain in energy efficiency by 2020. Governors could lower the 15 percent target to 12 percent with 8 percent efficiency gains if they determine the national goals are unattainable for their states.

* Obama's February budget envisioned $646 billion in revenue from the sale of the permits between 2012 and 2019. But that assumed a 100 percent auction of emissions permits, far from the level the House bill requires.

* Companies could offset up to 2 billion tons of their emissions annually by paying for green projects in the United States and other countries, such as preserving tropical rain forests.

* A clean energy bank within the Energy Department would be created to provide direct loans and government loan guarantees to encourage projects using clean energy technology.

* The Federal Energy Regulatory Commission would have greater authority to investigate manipulation in natural gas and carbon markets.

(Reporting by Richard Cowan in Washington; Editing by Mohammad Zargham)

Energy Barack obama Climate change Climate