32 Saying yes

Because Britain currently gets 90% of its energy from fossil fuels, it’s no surprise that getting off fossil fuels requires big, big changes – a total change in the transport fleet; a complete change of most building heating systems; and a 10- or 20-fold increase in green power.

Given the general tendency of the public to say “no” to wind farms, “no” to nuclear power, “no” to tidal barrages – “no” to anything other than fossil fuel power systems – I am worried that we won’t actually get off fossil fuels when we need to. Instead, we’ll settle for half-measures: slightly-more-efficient fossil-fuel power stations, cars, and home heating systems; a fig-leaf of a carbon trading system; a sprinkling of wind turbines; an inadequate number of nuclear power stations.

We need to choose a plan that adds up. It is possible to make a plan that adds up, but it’s not going to be easy.

We need to stop saying no and start saying yes. We need to stop the Punch and Judy show and get building.

If you would like an honest, realistic energy policy that adds up, please tell all your political representatives and prospective political candidates.

What Britain said yes to

A section added in the 2026 revision. This is the shortest chapter in the book and it makes three specific demands, on a premise worth checking too. Eighteen years is long enough to mark them.

“Britain currently gets 90% of its energy from fossil fuels.” In 2008 it was 92%. In 2025 it is 79%.1

That is real progress and it is slower than it sounds. Thirteen points in eighteen years, on a journey that has to end near zero, is a pace that finishes some time in the 2130s. And a fair share of the fall is the demand side rather than the supply side — total British energy supply fell from 9.19 to 6.29 exajoules, a drop of nearly a third, for the mixture of efficiency, cleaner electricity and offshored industry that chapter 15 takes apart.

“A 10- or 20-fold increase in green power.” British renewables went from 0.164 to 0.920 exajoules — a factor of 5.6. Counted as electricity rather than primary energy the multiple is larger, because wind and solar displace thermal plant at better than one for one. Either way Britain is somewhere between a third and two-thirds of the way to the bottom of the range he asked for, in a bit under half the time available. This is the demand he has come closest to meeting, and it is the one everybody said was impossible.

“A total change in the transport fleet.” Chapter 3 records that electric cars work and are arriving; chapter 20 records how little else has moved. Transport is still 2.71 EJ of oil, essentially unchanged in share.

“A complete change of most building heating systems.” Chapter 7 records the position, and it is the weakest of the three. Britain sits near the bottom of the European table for heat pump installations per household, and about two homes in five are below the fabric standard that would let one work well.

So: one demand substantially met, two barely begun, and the premise moving slowly. For a book that was widely read as pessimistic, that is a better record than its author would have predicted, and a worse one than the country needed.

And the “no” turned out to be bigger than he thought

MacKay’s diagnosis is public opposition — “the general tendency of the public to say no to wind farms, no to nuclear power, no to tidal barrages.” He is right that the “no” is the binding constraint. He is wrong about where it lives.

This edition has found the same shape in chapter after chapter, and almost none of it is the public in the sense he means:

  • Chapter 24. Nuclear’s cost is capital, so its price is a statement about the discount rate. On overnight construction cost — the same basis for both — Chinese units cluster near $2 a watt while Western ones scattered up to $6–15, and the difference is a standing workforce, a repeated design and a regulator that does not reopen it each time.
  • Chapter 25. Britain was offered 3.6 GW of Moroccan sun, engineered and through planning, and declined it in June 2025 because it preferred the electricity to be domestic. Sweden refused a cable to Germany; Norway is discussing switching two off.
  • Chapter 26. Five days of storage would cost about one nuclear power station and is not being built, because no arrangement exists under which anybody would be paid to own it.
  • Chapter 20. Nuclear merchant shipping is blocked by a liability convention that was written in 1962 and never entered into force. Insurers cannot price a risk when they cannot tell which regime applies.
  • Chapter 29. The carbon price arrived and worked at the margin; the transformations came from regulation applied at the point of manufacture.
  • Chapter 23. Capture works, and after thirty years it removes about one part in seven hundred of the carbon the energy system emits.

The word for all of these is still “no”. It is just not a member of the public saying it. It is a planning inquiry, a grid connection queue, a cost of capital, a procurement rule, an unratified treaty, a missing market. MacKay imagined the obstacle as an argument to be won. It turned out to be an institution to be rebuilt, which is harder, slower and much less interesting to write about.

What the arithmetic is for

Which brings this edition back to the thing the book is actually for, and the reason it has survived being wrong about so many numbers.

MacKay’s claim was never that his figures were right. It was that a plan has to add up, and that anyone who will not do the arithmetic is not making a plan. Eighteen years have moved almost every number in this book — solar by a factor of ten downwards, nuclear by a factor of ten upwards, British consumption per person by 44%, and the whole storage question from a cost problem into a market-design one. Not one of those changes touched the method. They were all discovered by doing exactly what he did: writing the quantity down, in a unit a person can hold, and checking whether the columns balance.

That is why the corrections in this edition are offered in his own units and against his own tables rather than as a replacement for them. The numbers were the perishable part. The insistence on having numbers at all is what has lasted, and on the evidence of the last eighteen years it is needed more now than when he wrote — because the arguments that stop things being built are now mostly arguments in which no quantity is stated at all.

So the closing instruction stands, with one addition. Stop saying no; get building. And when somebody tells you a thing cannot be done, ask them for the number.

  1. British figures are from the Energy Institute’s Statistical Review of World Energy 2026. Total energy supply fell from 9.19 EJ in 2008 to 6.29 EJ in 2025. Fossil share — oil, gas and coal as a proportion of total energy supply — fell from 92% to 79%; MacKay’s “90%” is close enough to the 2008 figure on any reasonable boundary. Renewables consumption rose from 0.164 to 0.920 EJ, a factor of 5.6; hydroelectricity is counted separately in that series and adds 0.02 EJ, and the Review reports non-fossil electricity on a substitution basis in some tables and a direct basis in others, which changes the multiple. Counted as delivered electricity the increase is larger — chapter 27 gives wind at 3.5 and solar at 0.8 kWh/d per person against essentially nothing in 2008 — so the “5.6-fold” figure should be read as the conservative end. Coal consumption of 0.05 EJ in 2025 is residual industrial use; coal-fired electricity generation ended on 30 September 2024.↩︎