Nuclear (in)flexibility, nearly 100% electricity from solar PV and offshore wind surge!

David Toke, Dec 08, 2025

I keep hearing claims, most recently from the British Government, about how nuclear power can be used flexibly to help balance fluctuating wind and solar. But in reality in most situations around the world nuclear is inflexible and its operation simply pushes wind and solar off the grid. Also, according to a report from Ember, cheaper batteries and proliferating solar can lead to solar on its own cheaply providing all electricity demand for 97-99 per cent of the time in the sunnier parts of the world. Meanwhile back in the UK offshore wind is now surpassing generation from natural gas according to the Energy and Climate Intelligence Unit (ECIU).

Tales of SMRs nuclear (in)flexibility

Looking around the world, it is very difficult to find any examples of nuclear power being flexible. The main example quoted is France. However, France has some close connections with the rest of the European continent. These differ for example, to the connections to the UK and the continent.

Unlike the UK, the French electricity system operator has no choice but to order the scaling down of some French nuclear plant. This is to cope with inflows of wind and solar across its borders that they cannot stop. In Britain where the inflows can be better controlled, as elsewhere, nuclear operators would prefer not to be flexible. Instead, wind and solar power get turned off and the renewable sources are blamed for energy that is really being wasted by inflexible nuclear operations! A study of Scotland, where a lot of wind power is constrained because of a lack of grid capacity, found that most wind power would not have been be wasted if there were no nuclear power station s operating in Scotland (see HERE). And, in practice there is no chance of nuclear power plant being flexible in normal operations, whatever people say!

The current UK Government is struggling to mask the fact that it’s so-called new generation of ‘small modular reactors’ (SMRs) is going to cost even more, MW for MW, than the much-overpriced Hinkley C and Sizewell C Nuclear plant. Rolls Royce is leading the charge here with a proposed 470MW (not small!) nuclear reactor. This will come into operation sometime in the next 20 years or so. According to Rolls Royce this development will be ‘equivalent to more than 150 onshore wind turbines’‘ (See HERE) Ah, so that’s the crack! SMRs are now promised to replace wind turbines! That will please the wideley expected future leader, Nigel Farage! Nigel hates windfarms but loves Rolls Royce and nuclear stuff – so patriotic, he claims!

I must say, it’s pretty small fare. I mean the Rolls Royce ‘SMR’ will only replace 150 onshore wind turbines – and at double or probably triple the price of onshore wind in delivered energy! (currently there are over 11000 wind turbines in the UK). Not much of a bargain really for Nigel, there I’m afraid. But really, as with populists the world round, its the headlines that matter, and never mind the facts!

Of course, as with other policies the Government is struggling to compete in messaging with the far-right. In doing so it feels it has to buy into a lot of myths about nuclear power. As one Government minister was made to say recently (presumably by his pro-nuclear civil servants) in an answer to a Parliamentary Question from a Liberal Democrat MP:

‘The next generation of nuclear, including small modular reactors (SMR), offers new possibilities including faster deployment, lower capital costs, and greater flexibility…..Whilst nuclear energy has a unique role to play in delivering stable, low carbon baseload energy, SMRs may be able to serve the electricity grid more flexibly than traditional nuclear, as well as unlock a range of additional applications in energy sectors beyond grid electricity.’ (See HERE)

What unbelievable nonsense! I would never want to be a government minister and have to spout such rubbish! I’ve already suggested that the SMR(s) will take a long time to emerge at eye-watering cost. But flexibility? Why should this happen? It does not happen now with the PWR plant at Sizewell B. So why should it happen with the Rolls Royce ‘SMR’ which is also a PWR? No reason at all!

In fact the Rolls Royce ‘SMR’ it is even less likely to operate flexibly than Sizewell B (which does not). This is because of the likelihood that, as in the case of Hinkley C, Rolls Royce will be offered a so-called ‘baseload’ contract. This means that the nuclear power plant are paid a set price for every MWh they generate – whenever it is generated. It does not matter whether wholesale prices become negative and wind and solar is forced off the system, nuclear continues to generate.

Rolls Royce will no doubt be given such a contract to ensure that the investors get a virtually guaranteed return. Otherwise it will be virtually impossible to attract private investors to give the required facade of part-private finance to the operation. In reality of course the bulk of the money to finance the equity for the plant will come directly from the taxpayer and the consumers will pick up the bill for the inevitable cost overruns.

To cap it all, the SMR(s) will contribute practically nothing to balancing renewables since that will be done by ‘peak’ gas plant (see my blog post HERE).

Almost 100 per cent 24/7 electricity from solar + batteries

Meanwhile solar PV is advancing around the world at several times the pace of new nuclear and fossil fuel power plant. See my earlier blog post HERE and the Figure below. Now, the energy think tank ‘Ember’ (see HERE) conclude that almost 100 per cent electricity can be delivered cheaply in the sunnier parts of the year using solely solar PV and batteries.

In places like Las Vegas and Oman 97-99 per cent of all electricity demand, 24/7 can be provided solely by solar PV for a cost of $104 per MWh. That is exactly the wholesale power price in the UK. It should be recalled that they are talking about just solar PV and batteries, never mind other renewables………………………………………………………………………………… https://davidtoke.substack.com/p/nuclear-inflexibility-nearly-100