But although the rapid upswings in demand won't result in supply problems unless they coincide with significant plant outages, they could still put power systems under considerable strain, players told Montel.

Energy consultants Inenco told Montel that the UK system was particularly vulnerable as millions tuned in to watch England on television and increased their energy use during half-time and after the match.

"From previous experience of England games we would expect an increase in demand of around 2 GW during the game," said Inenco spokesman Ian Parrett.

"However, for key games like in the 1990 World Cup, when the team reached the semi-finals, we saw an increase of nearly 3 GW. If a couple of plants came off line there would be significant pressure on the system."

Parrett said the UK system was already operating at almost half the normal spare capacity level because of routine maintenance, making England's opening match against the USA on Saturday a possible cause for concern for the network manager.

"National Grid likes to run at 8 GW of spare capacity to insulate us from any unexpected shocks. But for the next week we're predicted to be running at 3 GW below adequacy levels - as we're in the tail end of maintenance season."

TSO National Grid would bring additional generating capacity online to cater for demand surges - but that could drive electricity prices up, Parrett added. "If this happened the price would be affected, we've seen that with last winter's cold snap."

Demand hikes of up to 10% expected

M&C Energy Group analyst David Hunter told Montel it was highly unlikely the UK would be "caught short" on power supply, although said the size of the grid's challenge to cope with "TV pickups" would increase if England progressed through the tournament.

"Given population growth since 1990, the demand surge if England got to the final could represent an instantaneous hike of as much as 10%," said Hunter. "[But] it will also help that the matches England would be likely to play in the later stages are at 'off peak' times for industry," he added.

A spokesman for National Grid said that the challenge of coping with rapid and abrupt drops and surges in power demand required careful attention.

"The World Cup is always a time when you get large TV pickups in demand and we're gearing up for that," said Larque. "The demand in itself isn't the problem; it's that the demand is suppressed and then suddenly goes much higher. But we've forecast what the demand will be and we're making sure there'll be fast [-responding], efficient plant available."

Continental Europe expected to cope

Meanwhile, any surge in demand is not expected to have a significant effect on power demand in continental Europe.

"There will definitely be lower consumption on Friday 18 June when Germany play Serbia at 13:30 CET," said Berlin-based analyst Konstantin Lenz at Markedskraft. It was likely to exacerbate the pattern of lower demand on Fridays, he added.

However, at half time the water used to flush toilets could lead to strong surge in electricity use, he added. "But this will only last for about 15 minutes and will not have a large effect," said Lenz.

"These things usually have a small effect because of people switching on their TVs at the same time, but nothing dramatic," said a continental analyst.
"These events mostly occur outside the regular peak hours (e.g. 12 noon), so it should not have a problematic effect," he added.
Electricity demand would hardly be affected, said one trader; "only beer demand".

"I don't think we'll notice anything on the spot markets," he added. "The UK balance energy prices could move up if England reach the final. All the country's TVs running, with everyone opening the fridge at the same time at half-time."

The one-month long World Cup tournament  kicks off on Friday when World Cup hosts South Africa play Mexico.