Editor’s Note:This is one in a series of stories in which we look back at key issues and events of 2014 and why they will continue to make headlines in 2015.

Road tripping used to feel like it broke the bank, with gasoline prices in many places hovering above $3.50 per gallon or higher. Today, filling up for more than $2 per gallon in some places feels jarring.

Crude oil prices tumbled into an unexpected free fall in 2014, pushing gasoline prices down with them. Solar power prices continued their dive, too, helping usher in a new gold rush in renewables worldwide and predictions that in a major transformation of the U.S. electric power grids in just a few short years.

2014 set the scene for a major turning point in energy in 2015. We’ll see how those free-falling oil prices affect how people drive, and if that, in turn, will stunt use of public transportation and development of vehicles running on alternative fuels. The future of coal may be determined, just as solar power may start to spread outside California and Arizona and more deeply into places where the, thanks toand.

(MORE: )

The world is pinning its hopes on renewables to help cap CO2 emissions at a level that will prevent the globe from(3.6°F) above pre-industrial levels, the point at which the effects of climate change could spiral out of control, scientists warn. 2015 could also be the year energy policies aimed at curbing those emissions could show if they have teeth, including the Obama administration’s.

Scheduled to be finalized in June barring legal challenges, the Clean Power Plan is likely to see its approval complicated by that could define U.S. climate policies next year and for many years thereafter. Aiming to slash emissions from existing coal-fired power plants, the plan sends a strong signal to utilities thatare the federal government’s answer for how electric power companies should tackle climate change.

The natural gas that utilities will use to replace coal was itself the subject of a climate controversy that is likely to a major part of any ongoing energy conversation. Most natural gas is produced using, the same method energy companies use to extract the crude oil that ignited the shale oil boom of the past five years. Public health concerns associated with fracking prompted a ban in New York State, and study after study produced mounting evidence that large amounts of climate change-driving methane is leaking from both fracking operations and the natural gas distribution system leading to homes and power plants.

How those studies and low oil and gas prices will affect renewables will soon be readily apparent. Electricity generation from renewables was expected to grow by nearly 2 percent,and power generation from wind, solar and biomass alone was expected tofor the first time in history by the end of 2014. That growth is.

(MORE: )

New wind farm power generating capacity isin 2015, contributing nearly 5 percent of all U.S. power generation. Though solar power is expected to account for only a tiny fraction of power generation in the New Year —about 0.6 percent —growth is nearly inevitable as prices, which have fallen aboutsince 1998, continue to decline.

The future of carbon capture and storage technology may also become more clear, with the first large-scale coal-fired power planttechnology completing its first year of operation in Canada and research continuing onto make that carbon capture economical and effective.

If all those scenarios play out over the next year, one of the big stories next December will be how U.S. CO2 emissions from burning energy didn’t increase at all in 2015 —good news for the climate at a possible turning point in American energy.

Best of Energy Coverage From 2014:

MORE ON WEATHER.COM: 10 Worst CO2 Power Plants