What are marginal costs?

In economics, marginal cost is the cost of producing one additional unit of a good. For a coal plant, every additional kilowatt-hour requires more coal to be mined, transported, and burned. For a gas plant, more gas must be purchased on volatile global markets. For a nuclear plant, more uranium must be enriched and spent fuel must be stored.

For a solar panel or a wind turbine?

Nothing.

Once the panel is on the roof and the turbine is spinning, the fuel — sunlight, wind — is free. There is no commodity to buy, no supply chain to secure, no dictator to negotiate with. The marginal cost of producing the next kilowatt-hour approaches zero.

This is not a minor economic detail. It is a fundamental paradigm shift.

The economics of fossil fuels: a treadmill

Fossil energy is a flow cost system. You never stop paying:

  • Coal must be mined continuously. Mines degrade. New seams must be opened.
  • Gas must be drilled, fracked, liquefied, shipped, regasified. Pipelines must be maintained — or, as Europe learned the hard way, can be cut off overnight.
  • Oil markets are subject to geopolitical games, OPEC decisions, wars, and speculation.
  • Uranium must be enriched, and the waste remains dangerous for geological timescales.

Every kilowatt-hour from fossil sources carries a variable cost that depends on global markets you do not control. When Russia invaded Ukraine, Europe’s gas prices quadrupled within months. No country that relies on fossil fuels is truly energy-sovereign.

Renewables: pay once, harvest forever

Renewable energy inverts the cost structure. It is a capital cost system:

  • The investment is upfront: manufacturing, installation, grid connection.
  • After that, operating costs are minimal — maintenance, cleaning, occasional component replacement.
  • There is no fuel cost. Zero. For 25 to 30 years or more.

To be fair: maintenance costs are real. Inverters need replacing, panels need cleaning, wind turbines need servicing. These costs are not zero — but they are predictable, modest, and declining. They are nothing compared to the perpetual fuel bill of a fossil plant.

And here’s the thing that rarely gets mentioned: the “end of life” of a solar module or a battery is not the end of its function. After 25 or 30 years, a solar panel doesn’t stop working — it just produces somewhat less. Typical degradation is around 0.3–0.5% per year. A panel at “end of life” still delivers 80–85% of its original output. And it keeps going. For how long? Nobody actually knows yet — because we haven’t reached that point. The oldest panels in the world, installed in the 1980s, are still producing electricity. At this point, the evidence suggests that solar modules and batteries will outlive their warranty by a wide margin. That is a remarkable property for an energy source.

This means that the more renewable capacity you build, the cheaper your system becomes over time. The learning curves for solar and wind have been relentless: solar module prices have dropped by over 99% since 1976. Wind energy costs have fallen by roughly 70% in the last decade alone.

And unlike fossil fuels, these costs only go in one direction: down.

What near-zero marginal costs mean in practice

Price stability

Fossil fuel electricity prices fluctuate with global commodity markets. Renewable electricity prices are determined at the moment of investment and then remain essentially fixed. A solar farm built today locks in its generation cost for decades. No price shocks. No inflation exposure. No geopolitical risk premium.

Abundance instead of scarcity

Fossil energy economics is based on scarcity: limited reserves, extraction costs, transport bottlenecks. Renewable energy economics is based on abundance: the sun delivers roughly 10,000 times more energy to Earth’s surface than humanity uses. Wind is a consequence of solar heating and will blow as long as the sun exists.

When your marginal cost is zero, the economically rational response is not to restrict supply — it is to maximize deployment.

Deflationary pressure on electricity markets

We are already seeing this effect: on sunny, windy days, wholesale electricity prices in Germany, Spain, and other countries regularly drop to zero — or even go negative. The more renewables on the grid, the more often this happens.

This is sometimes framed as a “problem” (the so-called “cannibalization effect”). But it is only a problem if you insist on running a market designed for expensive, scarce energy. In reality, it is a signal: the system is telling us that electricity wants to be cheap. We should listen.

Electrification of everything

When electricity becomes radically cheap, it makes sense to electrify everything: heating, transport, industrial processes. Heat pumps replace gas boilers not because of ideology, but because the economics are overwhelming. Electric vehicles replace combustion engines not because of regulation, but because the fuel cost drops by 80%.

Near-zero marginal cost electricity is the foundation of a fundamentally more efficient economy.

The insanity of not going renewable

Given all of the above, consider what it means to not invest in renewables:

  • You choose permanent fuel dependency over energy freedom.
  • You choose volatile prices over stable costs.
  • You choose geopolitical vulnerability over sovereignty.
  • You choose rising costs over falling costs.
  • You choose a resource that depletes over one that renews.
  • You continue to pay for every single kilowatt-hour forever, instead of paying once and harvesting for decades.

And on top of all that, you continue to destabilize the climate.

There is no rational economic argument for this. There is no rational strategic argument. There is no rational engineering argument. The only arguments left are inertia, lobbying, and ideology.

But what about storage? What about grid costs?

Yes, renewables need storage and grid infrastructure. These are real costs. But consider:

  • Battery prices have fallen by over 90% in the last 15 years and continue to drop.
  • Grid expansion is a one-time infrastructure investment — not a recurring fuel cost.
  • Fossil fuel systems also need grids, pipelines, refineries, tankers, and storage — we just don’t question those costs because we’re used to paying them.

The total system cost of a renewable energy system — including storage, grids, and flexibility — is already competitive with fossil alternatives in most regions. And while fossil system costs will rise (depletion, carbon pricing, environmental damage), renewable system costs will continue to fall.

The bottom line

The marginal cost revolution is not coming. It is already here.

Every solar panel installed, every wind turbine erected, every battery connected is a step toward an energy system where the fuel is free, the prices are stable, and the air is clean.

Not investing in renewables at maximum speed is not cautious. It is not pragmatic. It is not “balanced.”

It is, by any economic measure, insanity.