Why Solar Panels Still Work on Cloudy Days

Apr 01, 2025

🌫️ “So... You Just Bought a Really Expensive Roof Ornament?”

That was the first thing Haruto's neighbor said when he walked over.

It was early morning in Daly City, California—the fog capital of the West Coast. Thick grey skies hung over the neighborhood like wet wool. You couldn’t see the sun, let alone feel it.

Haruto stood on his driveway, arms crossed, staring up at the glinting solar panels freshly installed on his modest home. They looked beautiful. Clean. Modern. Hopeful.

But now, with the fog rolling in and a skeptical neighbor smirking next door, Haruto was starting to second-guess everything.

“Do these even work,” he wondered aloud, “when it’s like this?”

He had asked the question before. In the webinars. During the consults. But he never quite got a straight answer—just cheerful reassurances and phrases like “great year-round performance.”

So he decided to find out the truth for himself.

🔍 Meet Haruto: Engineer Turned Skeptic Turned Advocate

Haruto Nakamura wasn’t afraid of tech. He worked in hardware design. He understood circuits, efficiency, light absorption. But when it came to residential solar, what he wanted was clarity, not marketing gloss.

Everyone around him seemed to believe the same myth: If it’s cloudy, your solar panels are useless.
But was it true?

He started tracking his solar production—every hour, every weather change. He logged it in a spreadsheet, cross-referencing it with cloud cover data from NOAA.

And within a week, he was seeing a pattern no one talks about loudly enough:
Cloudy days don’t stop solar. They just shift how it works.

☀️ The Insider Truth: Solar Doesn’t Need Direct Sunlight to Work

Here’s what Haruto confirmed—data in hand:

Solar panels work by capturing light, not heat. That light doesn’t have to be direct sunlight. Even under heavy clouds, solar panels can absorb diffused sunlight—the kind that bounces and scatters through the atmosphere.

On a fully overcast day, a typical system can still generate 10% to 25% of its full output. On bright, cloudy days—think high clouds or fog with some sun bleeding through—output can hit 40–60%.

And in certain conditions, especially cooler climates, solar panels actually perform more efficiently under cloud cover than in extreme direct heat, because overheating reduces voltage.

“It’s not all or nothing,” Haruto realized. “It’s a curve.”

But that wasn’t the only insight he uncovered.

🧠 Cloudy Regions Still Go Solar—and Win

He started studying solar adoption rates around the world. The real shock?

Germany—a famously grey country with fewer sun hours than much of the U.S.—has been a global solar leader for over a decade.
Seattle, with nearly 226 cloudy days per year, has strong residential solar growth, thanks to net metering and smart design.
Even Tokyo, Haruto’s hometown, has embraced solar at scale despite humidity, haze, and limited rooftop space.

What these regions understood—and what most homeowners don’t—is that solar isn’t about chasing perfect days. It’s about optimizing for every day.

🛠️ How Haruto Reframed His Solar Design for Fog

Instead of buying a bigger system and hoping for the best, Haruto got strategic:

He worked with a local energy consultant who helped him:

Re-angle the panels to maximize diffused light from typical cloud paths
Invest in microinverters rather than a string inverter, so each panel could work independently—even if one was shaded or underperforming
Use solar output forecasting tools to understand seasonal production variation and plan energy use accordingly
Layer in time-of-use rates, so even on low-output days, he was saving money by using solar during off-peak hours

He also added a small battery system, allowing him to store excess energy on sunnier days for use during those foggy morning stretches.

His energy bill dropped. His confidence grew. And the neighbor? He came over a month later asking for a referral.

🌦️ The Transformation: From Foggy Doubts to Full Power

Haruto didn’t just install a solar system.
He learned it. Modeled it. Made it his.

Today, his panels continue to generate—even in the fog. On stormy weeks, they still chip away at his grid demand. And on clear afternoons, he stores what he doesn’t use.

He no longer worries about “bad weather days.” Because he knows: it’s not about perfect sunlight. It’s about a consistent, optimized system working quietly, steadily, in all conditions.

💡 Final Takeaway: Don’t Let Clouds Block Your Energy Future

The myth that solar doesn’t work on cloudy days is one of the biggest barriers to adoption. It stops people before they even ask real questions.

But the truth?
Solar works through clouds. Not despite them.

If you live in a cloudy or foggy region, what matters most is smart system design, informed expectations, and a partner who understands how to model your site for real-world conditions—not just blue-sky days.

“The sun is always there,” Haruto says. “Even when we don’t see it. So are the savings.”