Where solar takes us — and what you do next
The last decade was about proving what solar can do. The next will be about ensuring it becomes the world's leading electricity source.
This module covers the following six lessons:
New solar technology is just around the corner.
Existing solar PV + lithium-ion battery storage is already the cheapest new electricity in most of the world. Solar generation alone now clears at $30/MWh in China's cheapest projects and $50–80/MWh across the rest of the sunny world (Brazil, India, Oman, South Africa, Australia), rising past $100/MWh in the US where financing and interconnection costs drag the number up. Pair that with a four-hour battery and a well-designed system covers more than 95 % of demand around the clock at roughly $100/MWh in sunny regions. By 2030, the sunny-world generation mid-range is projected at $44–58/MWh. Cheaper than new gas, coal, or nuclear. This is not a wild forecast; it is on its way to being delivered.
As such, no new technology development is required for the transition to proceed; it is already proceeding on what exists. Every GW of solar and battery storage added this year drives their learning curves further, and the learning curve compounds.
That doesn't stop next-generation technology from being developed. Two strands extend the curve further — new cell chemistries and new ways of installing PV. Click a card below to see what each one enables and where it is in the deployment curve.
None of this is required for the transition. The current solar PV + lithium-ion stack is already cheaper than new gas, coal, or nuclear and shipping at scale. Perovskites, tandems, BIPV, and agrivoltaics will extend the curve further and faster.
The corporate scramble for firm clean power isn’t ideological. Global data-centre electricity demand is growing 12 % a year and is on track to double by 2030 (IEA). New gas plants now quote 5–7-year lead times — every utility on earth ordered turbines at once. A hybrid solar-plus-storage project builds in 1–2 years post-permitting. Solar + storage isn’t winning the data-centre buildout on principle; it’s winning it on the calendar.
The additional solutions needed where it's not very sunny.
Solar plus a few hours of lithium-ion storage can already meet most of the world's electricity needs. The exception is high-latitude grids, where the winter sun is so weak that hours of storage can't carry over into spring. The map below shows where. Each land cell is shaded by its seasonality indexThe lowest monthly output divided by the highest.. A value near 1.0 means output barely shifts through the year (the tropics); near 0 means winter effectively switches off (the polar regions). Most of the world sits above 0.5. The deep-blue band — northern Europe, Canada, northern Russia, Patagonia, the southern tip of New Zealand — is where the design problem actually lives.
GSA tiled · 0.5° Lowest monthly PVOUT divided by highest monthly PVOUT · every 55 km, real Global Solar Atlas data. Hover any city dot for its real 12-month curve.
Where seasonality is steep, five fixes combine to close the winter gap.
Diversify generation: wind alongside solar. Mid- and high-latitude grids get their strongest wind precisely when their sun is weakest — winter storms, longer nights, steeper pressure gradients. Wind and solar are seasonally complementary, which is why every serious northern decarbonisation plan builds both. The UK is already a working example: solar covers the summer day, offshore wind carries the winter. Solo-solar is a hot-country strategy; the high-latitude version is solar-and-wind.
North-south interconnection. High voltage transmission links move surplus from sunny latitudes into winter-bound ones. The proposed Morocco-UK Xlinks project and the Australia-Singapore Sun Cable are direct examples of this. But the dense web of existing EU interconnectors all runs on the same logic. Somewhere on the continent, the sun is shining or the wind is blowing. Long-distance transmission turns a local seasonal problem into a continental routing problem, and routing is solvable.
Slower phase-out of existing flexible generation. Gas peakers, hydro and nuclear do not need to retire on the same schedule as coal. Running them at low capacity factor for the handful of winter weeks they are needed is cheap, since the assets already exist. The avoidable mistake is decommissioning flexible plants before something has been built to replace them.
Overbuild and curtail. The cheapest long-duration solution is often no storage at all. Build solar and wind at two to four times average demand, accept that a chunk of summer output is spilled, and the rest carries far more of the winter than a system sized to average load. Curtailment looks wasteful, but at solar's current cost the spilled megawatt-hours are cheaper than the storage they would otherwise need. Most credible 100% renewables pathways for the UK, Germany, and the US lean on this lever heavily.
Long-duration energy storage (LDES) handles the residual. Lithium-ion dominates the 1–4 hour band today, with 8-hour systems already deploying in California and Texas; 12–16 hour li-ion will follow, and is on track to overtake pumped hydro as the largest form of grid storage globally within the next few years. Beyond that, the two technologies worth knowing are iron-airA battery that stores energy by rusting iron on purpose, then reverses the reaction to discharge. The materials are cheap and abundant; it is heavy and slow, which is fine for multi-day storage and useless for a phone. (cheap, heavy, around 100-hour duration, led by Form Energy) and flow batteriesEnergy sits in two tanks of liquid electrolyte pumped past a membrane. The tanks set how much energy you store and the membrane sets how fast you can deliver it, so you extend duration simply by fitting bigger tanks. (vanadium or zinc-bromine, power and energy scaling independently; commercial sweet spot 4–12 hours). Compressed air and gravity storage exist as niche options. The whole long-duration stack is roughly where lithium-ion was in 2010.
For most of the world, this lesson is academic. For high-latitude grids it is the design problem, and none of the five answers is exotic. All of them are being deployed today.
In this lesson you will see why solar and storage redraw the geopolitics of energy — and why a resource almost every populated nation already has changes the calculus of trade, dependence, and conflict.
Resource-based energy has shaped geopolitics for over a century. Control of oil reserves, control of pipelines, control of LNG terminals translates into coercive leverage. Wars have been fought over it. Solar and storage change the underlying geometry. Sunlight is weather, not geology — it lands consistently across a huge fraction of the earth's populated surface.
An energy-importing country can make big moves toward self-sufficiency by deploying solar and batteries at scale; a developing nation can leapfrog major fossil infrastructure entirely. That leapfrog is already happening at the smallest scale: solar home systems and mini-grids (Module 1, Lesson 5) are reaching households that were never going to wait for a national grid to arrive. As the world deploys solar and batteries at the scales already in motion, the ability of nearly every nation to generate its own power will be a profound force for good: less coercion, fewer resource wars, more autonomy.
The chart below shows how much of each resource the top five countries control. Reserves cluster in a handful of places; sunlight doesn't. Hover any bar to see which countries make up the top five.
Two recent crises showed what depending on a handful of suppliers costs.
In February 2022, Russia invaded Ukraine and cut gas exports to Europe. European wholesale gas jumped from about €20/MWh to over €300/MWh; UK power peaked above £500/MWh against a normal £45/MWh. Bills doubled, governments spent tens of billions shielding consumers. The US and Asia were largely spared.
In late February 2026, the US and Israel struck Iran. Iran closed the Strait of Hormuz, through which about a fifth of the world's oil must pass. Crude oil prices jumped around 50 % in a month to over $120/barrel. Every oil-importing country felt it: fuel, freight and gas prices all rose.
Both crises had the same cause: a few countries control most of the world's oil and gas. When they cut supply or block trade routes, importers pay.
The chart above plots both shocks. The navy line (European wholesale gas, left axis) sits near €20/MWh for years, spikes more than tenfold in 2022 after Russia cut exports, then settles. The red line (Brent crude, right axis) sits in a $60–90 band, then jumps to $126 in March 2026 when Iran closes the Strait of Hormuz. Two different commodities, two different crises — but the same issue for every importer.
The chart below shows how electricity bills differed nation-by-nation. UK wholesale power (amber) tracked gas all the way up to £508/MWh in August 2022. Spain (slate) stayed below €180/MWh from mid-2022, because homegrown solar carried more of the daytime load. In the 2026 shock both rose again, but so far only modestly.
Countries with serious solar and battery capacity weathered the worst of both shocks. As more transport, heating and industry shift from oil to electricity, oil price spikes will hurt less and less. A country running its cars, trucks, factories and homes on its own electricity is not exposed to the oil price at all.
Sovereignty doesn't mean every home off-grid. Cities and large urban centres still need transmission and firm capacity, and cross-border interconnection still earns its keep — weather is local, so a neighbouring country with sun or wind when yours hasn't is worth a wire. The picture is more distributed generation behind a smarter, still-interconnected backbone — less dependence on a handful of fossil exporters, not the abolition of the network.
The arguments most often raised against solar do not withstand scrutiny.
Most of the cases against solar are not really technical, they are decade-old talking points the data has overtaken. They still surface in policy debates, board papers, planning hearings, and dinner-table discussions, and they still slow projects, push up the cost of capital, and distort national energy strategy. Knowing how to respond to them is part of the job. Below are the ten you will meet most often and, in each case, the evidence that ends the argument.
Click any myth to reveal the reality. Click again to collapse.
None of these myths are harmless. Each one delays something measurable — planning officers anchored to 2010 cost figures slowing approvals, lenders and pension funds under-weighting solar, subsidy debates fought on premises the data overtook years ago. The cost is paid in projects not built, capital not deployed, and emissions not avoided.
In this lesson, you will see what happens as deployment approaches 10 times today's installed base.
Solar deployment is running at roughly 650 GW/year and accelerating. At 10× today's installed base (~30 TW), marginal electricity cost in most regions approaches near-zero for large portions of the day. This is not speculative — it's the arithmetic endpoint of the learning curves traced in Module 5 and the manufacturing scale from Module 7.
Very cheap energy unlocks things that weren't economic before. Desalination becomes a solvable engineering problem, not an intractable water crisis. Direct air capture of CO₂ becomes feasible when the dominant input cost (energy) drops far enough. Heavy industrial electrification — cement, steel, ammonia, chemicals — becomes justifiable where it wasn't. Energy-intensive activities relocate to where solar is cheapest, the way aluminium smelters followed cheap hydropower in the 20th century.
Implications for other generation are clear: nuclear ($141–220/MWh new-build, Lazard 2025) suffers from long timelines and no modular learning rate; gas survives only as a shrinking backup for rare low-solar events; coal is already uneconomic against new solar in most markets. Cities, large industrial loads, and high-latitude winters still need transmission, storage, and some firm capacity, but the energy system supplying these demand centres are going to radically change.
The interactive graphic below shows some of the changes predicted to occur as solar deployment progresses, and the rough timelines they may happen on. Drag the slider — or click any tier directly — to move between 1× (today) and 10×.
A note on the maths. The projection assumes today's solar deployment rate (currently around 650 GW/year) increasing by around 60 GW each year, and global electricity demand growing at 3% per year. It uses a 13% global-average capacity factor for solar. On that path, 30 TW arrives in the early 2040s and provides over 40% of a global grid that has by then grown to over 50,000 TWh (up from ~30,000 today). The cascade tiers above, and the dates attached to them, are our own projection from those assumptions rather than a published forecast — but the inputs are sourced. The IEA puts 2025 additions above 600 GW and cumulative capacity near 2,800 GW, and global electricity demand up 3% in 2025. Note that the same IEA outlook expects demand growth to average 3.6% a year to 2030: run the model at that rate instead and the arrival date slips, so treat the early 2040s as the optimistic end of the range. Deployment figures also vary by source and by whether capacity is counted DC or AC — BloombergNEF's 2025 estimate is nearer 700 GW DC.
Sources: IEA Global Energy Review 2026 (2025 additions, cumulative capacity); IEA Electricity 2026 (electricity demand growth); Lazard LCOE+ v18.0, June 2025 (nuclear and utility solar LCOE).
The deployment rate is the lever. Even with annual installs nearly tripling, demand growth still eats most of the new build, which is precisely why scaling solar now matters. Every year the install rate sits flat instead of climbing is an extra year of fossil infrastructure staying in the mix, and cumulative emissions stacking. The arrival date of "very cheap energy" is not fixed; it is set by how fast factories, finance, and permitting move in the next decade.
The payoff for getting there is wider than cheaper bills. Near-zero marginal energy for large portions of the day turns desalination into an engineering opportunity rather than a water crisis, brings direct air capture of carbon dioxide into the cost frontier, and makes green hydrogen — and the ammonia, steel, and shipping fuel built on it — economic. Space cooling becomes affordable in regions where heat is now lethal. The ~700 million people still without reliable electricity gain a route in that doesn't depend on building a fossil fuel plant first. Cheap energy is not a tidy efficiency story. It is what makes a long list of previously unaffordable good things possible.
In this lesson you pick the action that fits your situation, and walk away with a concrete three-step plan you can start this week.
You've finished the course. You understand the technology, the economics, the manufacturing, the lifecycle, the grid context, and the individual pathways. The last move is the one you make tomorrow morning.
There's no single right next step. Each of us starts from a different roof, a different rental, a different budget, a different appetite for change. Wherever you're standing today, there's a useful move you can make this week. Pick the path below that's closest to where you are, and you'll get a tailored three-step action plan: small, concrete, doable.
Six questions, the last a capstone. The course ends with an action, not an exam.
What already works is already enough. Solar PV + lithium-ion delivers more than 95% of demand in sunny regions at roughly $100/MWh around the clock — cheaper than any fossil alternative and shipping today. Perovskites, tandem cells, BIPV, and agrivoltaics extend the curve further; none are required to start.
Storage fills in behind it. Li-ion dominates 1–4 hour durations today, is deploying at 8 hours in California and Texas, and will almost certainly reach 12–16 hours in the next decade. Pumped hydro still covers around 90 % of installed grid storage globally where geography allows. LDES — iron-air, flow batteries, compressed air, gravity — is moving down its own learning curve and will handle the seasonal residual mainly in high-latitude regions. Most grids will be fine on Li-ion plus pumped hydro plus generous overbuild.
Energy sovereignty is the geopolitical pay-off. Reserves are geographic accidents that have driven a century of coercion and conflict; sunlight is weather, available across most populated latitudes. As solar and storage deploy at scale, nearly every nation gains the option to generate its own power — a profound force for good. Grids and interconnection stay (cities, large industry, and weather-sharing across borders all need them) but the underlying dependency on a handful of fossil exporters loosens.
At 10× today's deployment, marginal electricity in sunny regions approaches near-zero for large parts of the day. Desalination, direct air capture, heavy-industry electrification, and synthetic fuels all become economic. Cities, large industrial loads, and high-latitude winters still need transmission, storage, and firm capacity — the mix changes; the network doesn't vanish.
And the last move is yours. Homeowner: quote, roof, tariff, PV + battery. Renter: a community energy co-op. Business: a rooftop case and a PPA. Community member: a local planning consultation approached with informed questions. Whichever one fits, start this week.
You are now part of the solar and battery revolution.
Congratulations — you've finished all ten modules. You now understand how solar works, how it's built, how it's paid for, how it's scaled, how it's manufactured, how it lives and dies, how an individual deploys it at every scale, and where it takes the energy system next. The Monday-morning move is yours.
