* UK gas market undersupplied by 5 mcm/day
* Demand for gas-fired power generation up
May 18 (Reuters) - British wholesale gas prices fell on Wednesday on higher imports from Norway and ample supply from liquefied natural gas terminals, offsetting robust demand from gas-fired power plants.
Gas for immediate delivery fell 0.18 pence or 0.58 percent, to 30.65 pence per therm, while the day-ahead contract lost 0.43 pence or 1.39 percent, to 30.40 pence/therm.
With (Other OTC: WWTH - news) supply flows at about 229 million cubic metres (mcm) per day, and demand expected to be 234 mcm/day, Britain's gas system was 5 mcm undersupplied, National Grid (LSE: NG.L - news) data showed.
Traders said prompt prices eased on a comfortable supply outlook, offsetting higher demand for gas-fired power generation due to lower wind speeds.
Wind power output is expected to peak at about 3,400 megawatts on Wednesday compared with almost 9,000 MW of total installed capacity.
Norwegian gas supplies were up by 8 mcm to 31 mcm/day due to higher flows through Langeled, Britain's main gas import pipeline.
The Al Sheehaniya LNG tanker is expected to arrive to Dragon terminal on May 25 from Qatar, while three more tankers are scheduled to arrive in Britain by then.
Further along the curve, contract for gas delivery in June , was trading 0.28 pence lower at 29.52 pence/therm, gas for next-quarter eased by 0.30 pence to 30.20 pence/therm.
Longer-term prices, however, could gain support from the oil market later in the day as oil futures were trading near 2016 highs early on Wednesday, traders said.
The U.S. Energy Information Administration (EIA) is scheduled to release official storage data on Wednesday, and any further decline in stockpiles could push oil prices higher, ANZ bank said.
The Dutch day-ahead gas prices at the TTF hub fell 0.09 euro/MWh to 12.98 euro/MWh.
In the European carbon market, front-year allowances eased 0.13 euro to 5.92 euro a tonne. (Reporting by Nerijus Adomaitis in Oslo; editing by Jason Neely)