We saw an unexpected jump in prices this week. For this seven-day report period, the average price for natural gas on the NYMEX rose 6.7%. The 12-month average price for peak power on the PJM rose 3%.

It is hard to tie this week's price increase to any big news story. Perhaps the market place was concerned about the shrinking natural gas storage bubble. For example, did you know that on May 3, 2012, the natural gas storage surplus was 55% above the five-year average? As of today, thanks to below-average gas injections throughout the entire summer, the natural gas storage surplus is only 9% above the five-year average.

One big reason that the gas injections were far below average this summer was that electric power plants were switching from coal to gas. As the power plants burned natural gas to generate electricity, less gas was available for summer injections. Some reports show that the power plants consumed 25% more gas this year than last year, thanks to the retirement of the coal-fired plants.

Another possible reason for this unexpected jump in prices was the low natural gas rig count. The active U.S. gas rotary rig count experienced yet another slide from the previous week and settled at 452 active rigs for the week ending September 7, 2012. This count, 440 rigs lower than the same week last year, also sits 57% below the five-year average gas rig count of 1,047. Looking even further back, we see that natural gas rig counts are at a 13-year low.

Thankfully, the current energy prices still represent nine-year lows. However, keep an eye on the markets. This combination of below-average storage injections and consistently low rig counts could place upward pressure on prices.