LONDON: Prompt British wholesale gas prices rose on Thursday morning as low output from the country's wind farms ramped up demand for gas from power stations, leaving the system undersupplied.

The within-day contract was up 1.65 pence at 39.50 p/therm by 0919 GMT.

The day-ahead contract was up 0.65 pence at 39.50 p/therm.

Traders said gas demand rose as power plants sought to ramp up electricity production following a warning from the country's National Grid that electricity supply margins would be weak over the coming days.

National Grid said outages at some power generators combined with low wind power output spurred the weaker electricity supply margins.

"Margins remain adequate today, and we're continuing to monitor the situation for tomorrow and the weekend," the National Grid Electricity System Operator said on Twitter.

The day-ahead wholesale electricity price rose 7.25 pounds to 57.50 pounds per megawatt hour.

Analysts at Refinitiv forecast British gas for power demand at 66 million cubic metres (mcm) on Thursday, up 11 mcm on the previous forecast.

Peak wind power generation is forecast at 5.9 gigawatts (GW) on Thursday, falling to 2.9 GW on Friday, Elexon data showed.

Britain's gas system was undersupplied with demand forecast at 247.9 mcm and flows at 236.6 mcm/day, National Grid data showed.

Further out on the curve, prices also rose.

The November contract was up 0.40 p at 39.55 p/therm.

The Q1 2021 contract was up 0.50 p at 42.00 p/therm.

The day-ahead gas price at the Dutch TTF hub was up 13.95 euro at 0.20 euros per megawatt hour.

The benchmark Dec-20 EU carbon contract was down 0.64 euro at 25.11 euros per tonne.