Time to make 2025 updates to my annual “opinions about solar” thread. If you like these, you might like the second edition of my book, Solar Power Finance Without The Jargon. A 30% discount code WSQ0437 is valid on publisher website until end of Nov 2025.
It's the book I should have read before trying to get a job in renewable energy. Reviewers describe it as “to the point, important, and taught me a lot” and “surprisingly entertaining, don’t be put off by the title”.
https://www.worldscientific.com/worldscibooks/10.1142/q0437#t=aboutBook
I have put out this thread once a year on X since 2017 and Mastodon / Bluesky since 2024. See 2024 thread below, and from there links to previous threads. So you can see what I got wrong, or at least changed.
https://mastodon.green/@solar_chase/113214911341855405
Some of these assertions will contain links to BloombergNEF content under a paywall. If you are not lucky enough to have access, you'll have to believe me that's what it says.
Also, I'm on maternity leave, so this thread is lighter on changes than in some years.
Time to make 2024 updates to my annual “opinions about solar” thread.
If you like these, the second edition of my book, Solar Power Finance Without The Jargon is out.
https://www.worldscientific.com/worldscibooks/10.1142/q0437#t=aboutBook
1. To opinions! Solar is the cheapest source of bulk electricity in many countries, and the quickest to deploy, and now you couldn't stop it being built if you wanted to. The limits to PV build in most places are grid access, permitting, and sometimes installation labour.
2. 20 years ago when I got this job, I thought maybe solar would one day be 1% of global electricity supply. In 2024 it was about 7% worldwide, and rising fast. You can see this eating into fossil fuel power generation in, for example, Europe.
3. Solar will not solve every problem. But the biggest problem is that our civilisation relies on digging up fossil carbon and burning it, which is destabilising the climate, which multiplies a lot of very unpleasant threats. Solar is part of stopping us needing to do that.
4. We don’t need a solar technology breakthrough. The challenges to building solar are usually getting a grid connection and planning permission, or increasingly, power price cannibalization. Of which more later in thread.
5. Solar modules now cost 8.9 US cents per Watt (higher in US, India due to trade barriers). Solar panels are cheaper than most ordinary fencing materials. For rooftop installs, non-module cost is still $0.50-3.00 per Watt, so further module price declines make little difference.
6. These prices mean that few makers of solar modules are profitable right now. If manufacturers stop selling at these prices, they will permanently lose customers. They are locked into a game of chicken. There will be bankruptcies and eventual price stabilisation.
7. Solar manufacturing has always been a horrible business, and that’s unlikely to change. It’s very commoditised, barriers to entry are fairly low, and incremental improvements in cell and module tech make factories obsolete in less than four years.
8. India and the US have solar import tariffs, so modules are pricier there (~15 and ~27 cents/W respectively). Both countries are subsidizing local manufacturing capacity. This is a perfectly good strategy as long as it doesn’t slow down their energy transition, but...
9. Thank goodness we’ve collectively stopped the nonsense of boasting about "lowest ever solar auction prices", most of which were Middle East opaque transfer prices or had other features. PV power prices below $25/MWh unsubsidized are still too low. This is very cheap power, but solar still does cost money.
10. 'Power price cannibalization' for solar happens because solar plants in one area all generate at the same time. This means that they reduce the price of power at that time, “cannibalizing” their own revenues.
11. High solar penetration resulting in power price cannibalization also affects other power plants, but not as much as it affects solar, because solar plants generate most at times when solar is pushing the price down most. This will inhibit further solar build.
12. This is already obvious in Spain, California, Australia and even Germany. Now that the global liquefied natural gas price hike related to Russia invading Ukraine in 2022 has eased, lower power prices drive solar developers to seek long-term contracts again.
13. By 2030 most countries will have spot power prices of zero in sunny hours. This will be passed on to end consumers, to encourage them to shift power demand to sunny periods by electric vehicle and battery charging, preheating, precooling, etc.
14. Low power prices may be great for consumers but they are very bad if you're trying to build more clean power plants. Without demand-side flexibility, the energy transition will fail before fully pushing fossil fuel out of the mix.
15. It's very easy to say "but batteries!" and those are definitely part of the solution. California has over 14GW of batteries in a grid with roughly 50GW peak demand, and the reliability of the grid has improved as its carbon emissions go down.
16. ...but batteries are still small. In 2024, about 181GWh of lithium-ion stationary storage was deployed worldwide, plus 974GWh lithium-ion batteries in vehicles. (https://www.bnef.com/insights/37025).
Lithium-Ion Batteries: State of the Industry 2025 Dataset
This dataset provides an overview of electric vehicle and stationary energy storage battery demand and performance metrics across various sectors and regions. It acts as a summary of the data that BloombergNEF has on the battery industry in 2025.
17. Small-scale batteries are a thing too, even though the economics don’t always make much sense. 2024 battery attachment rates – proportion of residential PV buyers who get a battery too – were ~ 80% in Germany and Italy, ~ 50% in Switzerland, UK and California.
18. It is very difficult for installers and financiers to become large and long-term profitable in the residential solar and storage market. Margins are thin and there are diseconomies of scale.
19. In general this is a problem for solar, both for manufacturing and downstream: a distributed industry with low barriers to entry, and therefore few large firms, has little lobbying power. Industry associations work against this to represent the interests of renewables in politics, against those of more naturally consolidated industries like fossil fuels, but they do have a structural disadvantage.
20. There is no way we can build a big enough battery to shift energy from summer to winter. The economics of battery storage are nearly impossible at one cycle a year.
21. Everyone is defining 'long-duration storage technology' wrong. It's not about 6 or 8 hours — you can do that with lithium-ion and probably will — it's about having the capex to add more GWh of capacity decoupled from the capex of adding more GW.
22. Examples of real long-duration storage technologies are pumped hydro (reservoir size is decoupled from turbine capacity), or where the storage medium is big tanks of molten salt, or hot rocks. But all of these do still cost a lot of money if they are only cycling once per year.
23. Lithium-ion will probably continue to be the dominant battery technology. High prices for lithium in 2022-2023 drove interest in sodium-ion, and there are still products coming out, but new lithium production capacity has brought prices back down and so the impetus to switch has been reduced.
(The cure for high prices was, it turned out, high prices.)
24. We oughtta be building more wind generation capacity. Seriously, solar will get built anyway, but wind needs some help, and wind blows in the dark and in the winter. It doesn’t help that solar pushes down power prices and generates renewable energy credits (where relevant), which hurts wind farm economics.
25. To put it another way: when you tell an energy future model to optimise a power portfolio for clean power adequacy, it will give you more wind and less solar than when you tell it to optimise a least-cost electricity sector development.
26. BNEF’s New Energy Outlook modelling doesn’t want to just solve the intermittency problem with loads of batteries. This is because the batteries get lower utilization rates the more you build. Batteries cannibalize batteries long before you get 100% clean power.
27. Hydrogen made with renewable electricity will be used for steel and fertiliser manufacture. Some may be used to make shipping and aviation fuel. Some may even be burned for power in weeks of low renewables, which is one way to shift energy from summer to winter.
28. ...but sometimes net-zero electricity models want to put in hydrogen to cover weeks of low renewables just because the model isn’t given any other option. Deep decarbonization models do weird things. It may turn out there are easier pathways in practice.
29. Electrification of transport is far better than biofuels; solar plants can run an electric car on a small fraction of the land used to grow fuel to run a biofuel car.
30. Decarbonizing aviation is hard. The CEO of Lufthansa said in 2023 that running its fleet on sustainable aviation fuel made from electricity would take half Germany’s current electricity demand. BNEF thinks this an underestimate.
31. Direct electrification of aviation would be better. BNEF research did track orders for 989 electric aircraft (mostly small ones) as of early 2022, but this is a long term project. Fingers crossed. (www.bnef.com/insights/30267 ).
32. Heatpumps are better for heating homes than hydrogen, but in seasonal climates like northern Europe will exacerbate the seasonal demand and supply mismatch for solar. We need to build wind and probably nuclear as well.
33. How mismatched is European seasonal solar supply and electricity demand? Well, here is the situation for my fully electrified house in Switzerland with 13.2kW of solar, a heatpump and an EV. I would have needed about 122kW of PV to be self-sufficient across December.
34. Europeans shouldn't feel guilty about using electricity for airconditioning, it'll all come from the sun anyway by 2030. Solar generation times and seasons match airconditioning demand pretty well, which is good news for really hot countries.
35. Nuclear is safer than coal and climate change, and better than gas unless the gas plants are running very rarely. Batteries should help with the unfavourable ramping economics of nuclear (you *can* turn nuclear plants up and down, but you really don’t want to).
36. We’re finally getting serious about net zero carbon. Getting that last 5-20% of carbon out of power will be hard, and require some expensive solutions. The first 80-95% is easy-ish but we're getting on with it.
37. You can be cynical about government and corporate net zero emissions targets if you like, but they're a lot better than no net zero emissions targets.
38. Ordinary people have no idea how much progress we’ve made. Tell people at parties that UK carbon emissions in 2023 were at their lowest level since 1879, for example. Most developed economies are now reducing carbon emissions without lowering quality of life.
39. …It would still really help if rich people would stop pissing carbon into the atmosphere for no reason.
@solar_chase Could you say more about this some time? I've always wondered how the extra per capita carbon compares to how many fewer rich people there are
@dcporter it's not my area of study but - as people get richer they do emit more carbon (more driving, more flying, bigger cars, bigger houses to heat, often more meat consumption).
After that it becomes tenuous. The Oxfam study, for example, is fundamentally very flawed because it assumes the relationship between money and CO2 emissions continues all the way up. Which probably isn't true — spending money on, say, opera tickets or fine dining isn't the same as spending it on jet fuel...
@dcporter I am mainly being judgy about big cars and short foreign holidays here, to be honest. This is partly because neither appeals to me personally...
Jenny Chase
Dave Porter