Wholesale gas prices for immediate delivery turned negative on Tuesday [last week] as supplies surged in from the new Langeled pipeline from Norway.
Britain's gas storage capacity is 96% full so firms need to offload supplies.
As domestic gas bills are based on longer-term contracts, consumers will have to wait for big reductions.
After trading at an average of 26p a therm through September, the spot price for gas delivered immediately fell to -5p during the course of the day, meaning traders are paying to get rid of it.
Via Truck and Barter