Why a gas shock lifts your power bill even where gas barely runs

Climate & Energy 4 min 80 sources

The IEA says a Middle East gas-price spike is pushing electricity prices up worldwide - because in most markets the last, priciest unit needed sets the price every generator gets paid.

Key takeaways

The IEA says a Middle East gas-price spike has pushed electricity prices up worldwide, even as renewables set records.
In most power markets the last, priciest unit needed to meet demand sets the price every generator is paid - so a sliver of gas can lift the whole bill.
The same rule runs backwards: when cheap renewables cover demand, prices crash, and wind farms get paid to switch off.

The shock hiding in your electricity bill

The IEA, the West’s energy watchdog, published its mid-year electricity update on Friday, and it carries a paradox [8]. Global power demand is set to grow 3.6% this year and 3.8% next, up from 3% in 2025 [8]. Renewables are on track to pass coal as the world’s biggest source of electricity in 2026 [8]. Yet power got more expensive, not less.

The reason sits in the gas market. Disruption hit liquefied natural gas - LNG, gas chilled to a liquid so it ships by sea. As those flows through the Strait of Hormuz were squeezed, gas prices in Asia and Europe hit their highest since the 2022-23 crisis [8]. Some countries switched plants from gas back to coal; others brought in emergency measures to cut use [8]. A gas shock thousands of miles away showed up as a higher bill for people who mostly run on something else.

The last unit sets the price for all

Here is the mechanism, and it is worth slowing down for. Electricity is sold through an auction. Each generator says the lowest price it will accept to produce one unit [12]. Wind and solar, once built, cost almost nothing to run, so they bid cheapest, and nuclear comes next. Gas plants bid highest, because they must buy fuel and pay a carbon charge [12].

The grid fills demand from the cheapest bid upward. But the price everyone is paid is set by the last unit needed to meet demand - the marginal one [12]. So even if gas supplies just 1% of the power at a given moment, its price can rule. If it is the last plant switched on, its price becomes the price paid to every generator - the near-free solar included [12].

That is why the mix matters. In 2025 the UK made 31% of its electricity from gas; France made just 3%, running mostly on nuclear at 69% [12]. British households paid the fourth-highest electricity prices in Europe in the second half of last year [12]. The government will cut VAT - its sales tax - on home electricity from 5% to zero this October to ease the pain [12].

The same rule, running backwards

The rule cuts both ways. On a bright, breezy, low-demand day, cheap renewables can cover almost all the load. On 22 April this year, UK solar pushed the need for gas power close to zero [45]. When the last unit needed is a wind farm rather than a gas plant, the clearing price falls - sometimes to zero, sometimes below it.

At that point the grid has more clean power than it can use. British wind farms are already paid to switch off on such days, and so are generators in California, Spain and Australia [45]. One fix is to shift demand into those hours - paying people to use power when it is abundant, which can beat building storage or wasting the wind [45]. The abundance is real: in the US in May, solar generated more electricity than either coal or wind for the first time [26].

America’s version: a market for capacity

The United States runs a second auction on top - for capacity, the promise to be available. Its biggest grid operator, PJM, buys that promise years ahead, and it clears at a single price too. Data-center growth drove nearly half of the $63.6 billion charged across PJM’s last four capacity auctions [2].

The strain has turned political. FERC, the federal energy regulator, says PJM faces “a grave legitimacy crisis” and has given it until the end of September to reform or have reforms imposed [7]. President Trump, meanwhile, announced a voluntary pledge signed by more than 200 companies and 23 Republican governors to keep data centres from lifting household bills [55]. It is largely symbolic; power prices are mostly set by state regulators, not a White House promise [55].

When the cheap supply dries up

One last thread, under-covered. Serbia’s largest power plant, the Djerdap 1 dam on the Danube, has fallen to a third of its usual output as the river runs low [54]. It is generating about 5,000 megawatt-hours a day, its worst May and June since the plant opened in 1970 [54]. The low water even hurt a nearby coal plant, whose cooling system draws on the river [54].

When drought knocks out cheap hydro, the grid leans harder on the next unit up the cost ladder. The marginal plant creeps toward gas - and the price everyone pays creeps with it. Weather, war and demand all meet at the same place: the last plant switched on.

02 · Lesson · why it matters

Why the last, priciest thing running sets the price for everyone

In a market with one price for all, it isn't the average cost that sets your bill - it's the most expensive unit you still need.

The puzzle in the bill

Two facts sat side by side this week and seemed to argue with each other. In the US in May, solar generated more electricity than coal or wind for the first time. Worldwide, renewables are about to overtake coal as the biggest source of power. Clean electricity has never been more abundant or, per unit, cheaper.

And yet electricity got dearer, not cheaper, after a gas shock half a world away. Cheap power everywhere; a rising bill. That only stops being a contradiction once you see how the price is actually set.

One price, set by the last one in

Power is sold through an auction. Every generator names the lowest price it will accept for one unit. The grid then stacks them cheapest-first - wind and solar near zero, nuclear above them, gas near the top - and fills demand from the bottom up.

The trick is what happens next. The price is not an average of everyone who ran. It is set by the single last plant needed to meet demand - the one at the margin. And every generator gets that price. So a gas plant supplying the final one percent of demand can hand its high price to the whole grid, the near-free solar included. What you pay for is the most expensive unit you still need, not the cheap ones underneath it.

Why the cheap ones still collect the high price

That looks like a quirk. It is a design. A single clearing price is a rule someone chose, and it does a specific job. It hands every cheap generator the gap between its low cost and the high clearing price. On a gas day, the solar farm that bid near zero gets paid the gas price and keeps the difference.

That gap is not an accident to be scrubbed out. It is the reward that pulls money toward building more cheap power. So the same rule that stings you when gas is at the margin is the rule slowly funding the solar and wind that push gas off the margin for good. It serves the people who built the market, and it helps the people living under it. Both are true at once.

The rule doesn’t care which way it points

Watch it run backwards. On a bright, breezy, low-demand afternoon, the last unit needed might be a wind farm, not a gas plant. Then the clearing price falls to almost nothing - sometimes below zero, with wind farms paid to switch off because there is more clean power than the grid can use.

Same rule, opposite feeling. The price was never a measure of how much cheap power was on the grid. It was only ever about the one plant standing at the edge of demand. Move the edge, and the whole price moves with it.

Where you are standing in it

Your bill is set by the priciest plant running at your peak moment - not by the cheap afternoon solar you will never see itemised on the invoice. A war over a shipping strait. A drought that drops a river below its dam. A data centre plugged in three states away. Each one nudges which plant sits at the margin, and the margin sets your price.

You did not write that rule, and you cannot see it from your kitchen. Nor, really, can the people who run one plant, or one grid, or one country - each sees a slice of the stack, not the whole of it. So the honest version of “gas is why my bill is high” turns out smaller and stranger than the headline. The last unit is why. And almost nobody, standing anywhere in the system, can see the whole stack at once.

03 · Lab · your turn

Who Sets the Price

Stack power plants cheapest-first and see how the last unit needed sets the single price every generator is paid.

04 · Hope · carry this

The same rule that lets one gas plant set the price for a whole country is the rule quietly paying for every cheap solar and wind farm being built. Those farms are winning the long game, and each one built pushes the expensive plant at the edge a little further out.