(Bloomberg) -- The heatwave scorching London and southern England is threatening to worsen an energy crisis in a country where homes and businesses are struggling with gas and power bills.

High energy costs are fairly unusual in the summer in the UK because there aren’t that many homes running air conditioners and sucking in electricity. But the current situation is far from normal: British gas prices are triple the five-year average for the time of year, meaning any usage will be much more expensive than usual.

The energy market is also being strained by a heat-island effect where groups of big buildings stay warm and need more artificial cooling. Looking forward, as climate change makes extreme weather such as dangerous heat more common, the energy system will need to adapt to cope with the increased cooling demand.

For now, the grid is coping. But with the UK’s Met Office issuing an amber warning for London and southeast England as temperatures are set to peak early next week, here’s how the weather is taking its toll:

Wind and Sun

Heatwaves can be bad news for one source of cheap power: wind.

The high pressure system that’s causing the UK to bake typically weakens wind gusts that are crucial for spinning turbines that can at times provide the majority of the UK’s electricity. Wind-power production is forecast to slump this weekend as the mercury exceeds 30 degrees Celsius (86 Fahrenheit).

While this level of wind output isn’t unusual in summer, it puts more reliance on power stations that burn expensive and polluting gas.

On the other hand, clear and sunny skies are a plus for solar panels, but they produce much less electricity in the UK than wind farms can. There’s also some cloud cover in the forecast for the coming days, limiting the solar-power potential.

Heat Island

Although British homes largely get by in the summer without energy-intensive air conditioners, offices are another story. 

Demand is particularly high in built-up places like central London where large buildings create a heat-island effect, retaining heat overnight and staying warmer than the rest of the country. 

That need for power may intensify in the long term due to climate change, with the government predicting cooling demand to almost double by the end of the century.

“It’s not going to be so hot that everything falls apart,” said Nigel Arnell, professor of climate system science at the University of Reading. “But if I were running an energy company I’d be worried about increased demand during the working day.”

Hot Cables

The extra demand and heat also puts more pressure on power-grid cables. They get hotter the more electricity they transfer, and when air temperatures rise as well, that can limit how much power the network can carry.

“You have a double-whammy effect if you have air cooling driving up demand at the same time temperature is driving down the rating,” said Dave Openshaw, founder of consultancy Millhouse Power Ltd. 

For now, the network is prepared for such situations, especially as UK demand in the summer is still much lower than during winter -- and the Energy Networks Association said operations are currently running as normal. 

But as more people turn to air conditioning at home, further investment may be needed to keep the grid running smoothly, Openshaw said. 

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