The problem with intermittency of wind and solar energy is so obvious that you wonder why is has taken the Prime Minister this long to work out that we are going to carry on needing gas-fired power stations to fill in the gaps. In the case of solar energy this is, of course, every evening.

Rishi Sunak is quite right that Labour’s plan to decarbonise the electricity grid by 2030 (and apparently save us oodles of money off our bills in the process) is a ‘fantasy approach’. The trouble is, the government’s own approach isn’t a whole lot better.

If we are going to have a grid based on wind and solar, gas is pretty much essential

In spite of today’s announcement about new gas-fired power stations, the target of decarbonising the grid by 2035 (i.e. in 11 years’ time rather than 6 years’ time, as Labour proposes) seems to remain in place. In other words, by the time they are built, Rishi’s new gas power stations will be allowed to operate, at least in their initial form, for no more than a decade. And that assumes the increasingly unlikely outcome of a Conservative election victory. By 2035, the new gas plants will presumably have to be equipped with carbon capture and storage – which doesn’t yet exist in Britain in commercial form – or they will have to be closed.

It is one thing for the Prime Minister to announce the building of new power stations, but unless the government is going to build them itself, who is going to want to invest in new plant in such conditions? A new gas power station ought to last at least 30 to 40 years. If you know you are going to have to close it, or drastically alter it after just 10 years, you are only going to build it if you can be sure of an astronomical rate of return in the meantime.

That is not impossible, though, when you consider how gas plants are already being used. One of the reasons that electricity from gas plants is so expensive now is because the plants themselves are used intermittently: being turned on and off in order to balance the output from wind and solar. Gas plants, unlike nuclear plants, can at least be turned on and off in this way – but it is hardly the cheapest way to generate electricity. Not only is it thermally less efficient to operate them like this, but it is a lot less financially efficient to have a plant standing idle for much of the time compared with being able to operate it constantly. That is why gas plants charge high prices for power when they are needed.

If we are going to have a grid based on wind and solar, gas is pretty much essential. The only alternative is energy storage – forms of which are either fantastically expensive or simply untested. It is puzzling how Labour seems to think decarbonising the grid by 2030 will save consumers money when existing forms of energy storage, such as pumped-storage reservoir systems and lithium batteries, cost several times as much as generating the energy in the first place. Other potential solutions (such as using surplus power to produce hydrogen from electrolysis of water) do not yet exist in commercial form.

As Ofgem warned this morning (as if it wasn’t already obvious), the costs of Net Zero are bound to fall most heavily upon the poor: on people who cannot afford to invest in every saving technology. That is unchanged by today’s announcement on new gas power stations – and will remain the case whoever wins the election.