U.S. natural gas prices have fallen 30% since the start of the year as demand this winter fell to the lowest in four years due to the warmest weather on record in December, January and February.

Those low prices, however, may not last long since the low rates have already prompted power companies that can burn either gas or coal to generate more electricity with gas.

Since the start of the year, gas futures have collapsed by 30% to around $2.774 per million British thermal units (MMBtu) from a two-year high of $3.994/MMBtu on Dec. 28.

Futures averaged $3.58/MMBtu in December 2016, $3.29/MMBtu in January 2017 and $2.91/MMBtu in February 2017, compared with $2.04/MMBtu in December 2015, $2.23/MMBtu in January 2016 and $1.93/MMBtu in February 2016.

Even though gas was almost 60% more expensive this winter than last year due to lower production and rising exports, analysts said the power sector could boost its use of the fuel to the record high levels seen in 2016 if prices continue their recent downward spiral.

“The lower prices of late ... are already beginning to stimulate power generation demand ... We think power generation this summer could end up with only a small loss, or even a slight gain, over last year,” Martin King, director institutional research at GMP FirstEnergy in Calgary, said in a note.

Gas consumption by the four biggest users of gas—residential, commercial, industrial and power—fell to an average of 82.8 billion cubic feet per day (Bcf/d) from December 2016 to February 2017, its lowest level since the winter of 2012-2013, the data showed.

Over the past four winters, gas consumed by those big users reached 84.8 Bcf/d during the warm winter of 2015-2016, 89.8 Bcf/d during the second “polar vortex” winter of 2014-2015, a record high 91.4 Bcf/d during the first polar vortex winter of 2013-2014 and 81.1 Bcf/d during the warm winter in 2012-2013, Thomson Reuters data showed.

Gas-weighted heating degree days (HDDs), a measure used to estimate demand to heat homes and businesses, totaled 2,107 from December-February, according to Thomson Reuters data.

That compared with 2,124 during the same period in 2015-2016, a 10-year average of 2,440 and a 30-year average of 2,390, the data showed.

HDDs measure the number of degrees a day's average temperature is below 65 degrees Fahrenheit.

Meteorologists at the U.S. National Oceanic and Atmospheric Administration (NOAA) said the winter of 2015-2016 was the warmest on record in the contiguous U.S. states, according to data going back to 1895. NOAA has not yet released its final results for the winter of 2016-2017.

The U.S. is not alone in experiencing warm weather. Around the world, annual temperatures have increased in most years since the late 1970s, with eight of the past 10 years being the warmest on record, according to U.S. climate data.