How Many Solar Panels Would It Take to Power the World?

Humanity runs on roughly 20 terawatts of average power across all energy uses. Could panels alone supply it — and how much land would they actually need? The arithmetic is more interesting than the memes, and the free Solar Overbuild Calculator lets you run every assumption yourself.

Nameplate is not average

A panel's rating is its peak output; the sun sets, seasons happen. A real-world capacity factor of ~25% in good locations means delivering 20 TW average requires about 80 TW of nameplate — before storage losses. Add an overbuild factor of 1.3–1.5 so winters and cloudy weeks still clear demand, and you're building on the order of 100–120 TWp of panels.

The land answer

At ~220 W/m² of active panel and a 3.5× spacing factor for real solar farms, 100 TWp needs roughly 1.6 million km² of land — a square about 1,270 km on a side. That's enormous, and also just ~18% of the Sahara, or about 1% of Earth's land. The calculator reports the Sahara percentage live as you change assumptions, along with panel count in the billions and capex in the trillions.

What the objections get right — and miss

Storage is the honest objection: nights and winters need batteries or complementary sources, which the solar + battery math quantifies — it multiplies costs by 2–4×, not by absurdity. Materials are manageable: silicon is sand-abundant, and silver use per watt keeps falling. Transmission is real engineering but solvable with HVDC. The deeper point: at 2026 panel prices (~$0.62/W utility-scale), the panel cost of powering civilization — roughly $60–75 trillion spread over decades — is comparable to what the world already spends on fossil fuel extraction over the same period.

And then off-planet

Above the atmosphere there is no night, no weather, and ~36% more flux. That's why the same math scaled orbitally — see the Space Solar Power & Data Station designer and Constellation Energy-Grid model — is the logical end of the abundance curve.

FAQ

How many panels is 100 TWp?

At 550 W each: about 180 billion panels. World manufacturing capacity passed 1 TW/year around 2025 — so decades at current rates, or faster with expansion.

Could rooftops alone do it?

No — global rooftop potential is a few TW average at best. Utility-scale farms carry the bulk.