The sweeping energy and global warming bill taken up by the House on Friday was as complicated as it was contentious. The bill started the day at 1,200 pages — and that was before the House adopted a 300-page amendment.

Here's the Cliff's Notes version.

Q: What are the bill's major features?A: The centerpiece is a so-called "cap-and-trade" provision, which sets limits on the greenhouse gas emissions scientists blame for global warming. The goal is to reduce emissions to 17 percent below 2005 levels by 2020 and more than 80 percent below 2005 levels by 2050.

Q: How would that work?A: The bill would create a new system for buying and selling emissions permits which give the bearer the right to send carbon dioxide or other greenhouse gases into the atmosphere. Major sources of those gases, such as power plants and factories, would need to obtain enough permits to cover their emissions.Or they would need to cover their emissions with "offsets" — measures, such as planting trees, to scrub carbon dioxide from the sky or prevent emissions that otherwise would have occurred.

Q: Would those permits cost anything?A: No, not at first — at least not for most emitters. As part of a series of deals to attract votes by helping coal users avoid added costs and raising consumers' energy bills, lawmakers agreed to give most permits away for free at the start. Eventually, the government will sell them at auction.

Q: Anything else big in the bill?A: There's a lot. The bill requires states to generate an increasing portion of their electricity from renewable sources — most notably wind and solar energy — topping out at a 20 percent requirement in 2020. States could account for some of that target through energy efficiency.Other portions of the bill would set strict efficiency requirements that the government projects would dramatically curb American energy use. There are billions of dollars for research into so-called "clean coal" — as-yet-unproven technology to capture and store the carbon emissions from the power plants that are the leading source of global warming today.And there are scores of small-but-significant items, many added to bring certain constituencies or members of Congress on board. Those include tweaks to federal regulation of biofuels and coal power plants, incentives for plug-in hybrid cars and nuclear energy, upgrades to the electric grid, money for advanced energy research and, in a last-minute addition, rules to prevent homeowners' associations from banning their members' installation of rooftop solar panels.

Q: How will this affect the economy?A: Depends on who you believe. The White House and House Democratic leaders call this a "jobs bill" that will jump-start the "clean energy economy." The bill's components will force utilities to invest in wind, solar and other low-carbon energy sources, the Demo-crats say, creating jobs in the development, production and installation of things like wind turbines and solar panels.Republican opponents say the bill will kill "millions" of American jobs, by raising the price of energy. Manufacturers, they predict, will flee the United States for China, India and other developing nations that use cheap coal.

Q: What about my pocketbook?A: Again, big disagreement. The Environmental Protection Agency and the non-partisan Congressional Budget Office project the bill would cost the average American household less than $200 a year through 2020, due to higher energy prices.Some conservative think tanks predict a price tag more than 10 times that high — up to some $3,000 per year per family — when factoring in productivity losses from switching to more expensive energy sources.

— Chicago Tribune