In a bid to buy time, Drax has converted three of its half-dozen huge boilers to burn wood scraps imported from North America, instead of coal. The climate economics might seem elusive: The electricity produced this way is much more costly than coal-fired power and, like coal, the burned wood emits carbon dioxide. But the company receives generous subsidies from the government for this effort, on the rationale that wood is a renewable biofuel.

If British government policy on power plants seems rather experimental at this point — subsidizing some activities, while taxing or threatening to ban others — it might be because officials around the globe are grappling with a contradiction that is implicit in the Paris climate discussion: Even as the world tries to adopt cleaner forms of energy, the global demand for electricity is becoming increasingly voracious as more countries adopt the technologies and amenities of modern electronic life.

Eventually, other forms of power production might render obsolete the whole notion of a big electric utility provider like Drax — whether future electricity comes from many smaller-scale wind or solar sources, or from whatever new technologies might be dreamed up by the Breakthrough Energy Coalition that Bill Gates and other philanthropists announced at the conference.

“If you change the underlying economics of an industry, you change the structure of the companies,” said Dieter Helm, a professor of energy policy at the University of Oxford. “That is why you see the writing on the wall for the big utilities.”

Some big European energy companies are adapting by entering a new barter-type relationship with some electricity customers. Enel, the Italian utility, now has 600,000 business or residential customers generating some of their own power from solar panels or wind turbines. On sunny or windy days, these customers send power to the grid. When it is dark or calm, Enel provides the electricity.

Responding to flagging demand for fossil-fuel energy, Enel has already permanently shut two dozen conventional power plants. The company no longer sees itself as primarily an operator of power stations, said Francesco Starace, Enel’s chief. “We are providers of energy.”

But Britain, for now at least, needs the Drax plant, which has six boiler-and-turbine units that churn out enough electricity to supply nearly 8 percent of the country’s needs. And most other industrialized countries will still need their own big power producers for years to come. There are not yet enough wind turbines and solar panels on earth to meet the global demand for electricity.

Electric cars, for instance, are on the rise. So are electric-powered manufacturing processes like robotics and 3-D printing. Service businesses, ever more digitally driven, need their electrons to keep the data flowing. “Electricity is where it’s at,” Professor Helm said.

The priority, though, is phasing out power stations like Drax’s that are still heavily reliant on burning coal, the dirtiest and most carbon-emitting of fossil fuels. As China and India, each with more than a billion people, continue to industrialize, their officials say they have little choice but to continue burning coal as part of the energy mix. Whatever agreements might be reached in Paris, as much as 30 percent of the world’s electricity might still come from coal by 2040.

But Western industrialized nations, though they still rely heavily on coal for power generation, are intent on cutting back. About 25 percent of Europe’s electricity is still generated by coal plants, and in the United States the figure is even higher — around 40 percent — according to the International Energy Agency.

Aiming to cut those numbers, Western governments are using mixes of penalties and incentives to steer big power producers down the public-policy paths that regulators deem best.

In Drax’s case, government subsidies have induced the company to invest 700 million pounds, or about $1 billion, to reconfigure those three boilers so they can burn tree stumps, sawmill scraps and other wood products, mostly from the United States and Canada. The company has also built facilities in Mississippi and Louisiana to make wood pellets, which it ships to British ports, then hauls by rail to the Drax plant.

Drax, which is profitable these days, mainly on the strength of subsidies, would lose money on the electricity it generates by burning wood if the process were not being underwritten by the government.

“Our coal units are becoming increasingly marginalized,” Andy Koss, Drax’s chief executive, said in an interview here.

Government intervention cuts both ways. Mr. Koss said that coal was being squeezed out by power generated from government-subsidized renewable energy sources, particularly wind, and by rising penalties. That includes a recent near-doubling of the carbon tax that British utilities must pay, to £18 per metric ton of carbon dioxide emitted. Last year, Drax paid about £118 million in carbon taxes for its coal-burning boilers; the wood-fueled units are exempt from the tax.

The Drax power station, constructed in two phases in the 1970s and ’80s by the government and privatized in the ’90s, was the last coal-burning plant built in Britain. And though Drax has managed to substitute wood as a fuel, there are limits to how versatile a purpose-built coal plant can become. Converting to natural gas, which is cleaner than coal but still a carbon-emitting fossil fuel whose own future is uncertain, is not feasible for the company. Investors consider Drax’s prospects so shaky that its stock price has fallen by about 70 percent since the beginning of 2014.

The British government sees another source — nuclear power — as part of the clean-energy mix and is using subsidies to build new nuclear plants after a 20-year hiatus. While some other governments, including Germany’s, are abandoning nuclear power as too risky, the British authorities consider nuclear power a reliable and emission-free source of energy that can keep the lights on while renewables like wind and solar work out their teething problems.

But nuclear comes at a stiff price. The plant planned for Hinkley Point in southwest England is now projected to cost £18 billion. And British electricity bills may rise because the government is guaranteeing EDF, the French state-controlled utility that will build the plant, and its Chinese partners more than double the current price of electricity for the power it generates.

Some big power companies are making their own clean-energy pushes. SSE, a large British utility based in Scotland, has invested £4 billion in offshore wind farms and other renewable sources since 2008. “When I went into this industry from university, friends were talking about this staid, boring lifeless industry,” said Martin Pibworth, SSE’s director of wholesale operations. “It has been anything but staid, boring or lifeless.”

Drax wants to convert its remaining coal-fired boilers to burn wood pellets but has been unable to come to terms with the government on what it considers a sufficient incentive.

Mr. Koss said that Drax’s coal burners would probably eventually operate only during peak demand periods, like winter weekdays, when power commands a high price. By contrast, he said, the wood pellet units would probably run full-blast, nonstop for a decade or more because of the government support.

Environmental activists say subsidizing an operation like Drax makes little sense because the government is both encouraging the cutting of forests and helping to keep coal plants in operation.

“Burning wood for electricity is no less disastrous for the climate than burning coal,” a group called Biofuelwatch says on its website. “These conversions are really about keeping old, dirty power stations alive for longer, and cashing in on government subsidies.”

But utility-industry experts say critics need to understand that power companies and governments are still only groping their way toward the cleaner-energy future.

“This whole move to become environmentally more sound is going to go through a rocky transition period of 20 to 25 years,” predicted James Basden, who leads the utilities practice at the consulting firm Oliver Wyman in London. “But our grandchildren may look back and say thank you very much.”