* Output from various UK terminals down
* Heating demand expected to decline next week
Feb 17 (Reuters) - British gas for instant-delivery rose on Wednesday due to an undersuppled transmission network as several terminals cut output while demand for heating stayed high.
Gas for immediate delivery rose 0.25 pence at 30.25 p/therm by 0848 GMT compared to the previous settlement.
Britain's gas system was undersupplied by around 10 million cubic metres (mcm) on Wednesday. Demand is forecast at around 330.5 mcm/day - 48 mcm above seasonal normal demand - while flows are at around 320.2 mcm/day, National Grid (Amsterdam: NG8.AS - news) data shows.
Gas flows from the Barrow terminal are running at 1 mcm versus 4 mcm on Tuesday and 7 mcm typically, while flows from BP's Teesside terminal are down at 7.5 mcm from 9 mcm in the previous session.
UK Continental Shelf output is currently around 130 mcm/day - equal to Tuesday levels but 7 mcm down from Monday and 15 mcm down from last week, according to Thomson Reuters (Dusseldorf: TOC.DU - news) analysts.
Flows from Norway, however, remained strong at 68 mcm/day.
Gas demand for heating throughout this week is forecast to be 240 mcm/day, dropping to 215 mcm/day next week, analysts say.
Temperatures are forecast to be colder than normal this week. By the weekend, temperatures are expected to return to slightly above average levels.
Further along the UK gas curve, the Summer 2016 contract was 0.05 pence lower at 27.10 p/therm.
In the Netherlands, the day-ahead gas price at the TTF hub was 0.28 euros lower at 12.30 euros per megawatt-hour, also due to increased consumption.
In the European carbon market, front-year EU allowances were up by 0.04 euros at 4.74 euros a tonne. (Reporting by Oleg Vukmanovic in Milan) ))