How much does fog reduce solar panel output?

Fog reduces output to 5–15% of peak — similar to heavy rain. The impact is temporary (fog typically clears within hours). Over a full year, fog accounts for less than 1% of total output loss.

Is fog worse than cloud for solar panels?

Fog reduces output more than most cloud cover (5–15% vs 10–30% for heavy cloud). However, fog is less common and typically clears faster. Cloud cover has a larger total annual impact because it occurs more frequently and can persist all day.

Should I worry about fog when considering solar panels?

No. Fog has a negligible impact on annual solar output (<1%). All savings estimates already account for UK weather including fog. The decision to install solar should be based on roof direction, system size, and cost — not fog.

Do Solar Panels Work in Fog?

Q: Do solar panels work in fog?

Yes, but at very low output (5–15% of peak). Fog significantly reduces light intensity. However, fog typically clears by late morning, after which panels generate normally. Annual output lost to fog: approximately 0.5–1%.

Last updated: 18 March 2026

Independently written

Solar panels in misty conditions — reduced but not zero output — Fog reduces light levels significantly — but panels still generate some electricity.

Do solar panels generate electricity in fog?

Solar panels produce 5–15% of their rated output in fog. Fog significantly reduces light intensity, but some diffused light still reaches the panels. In the UK, fog typically clears by late morning, after which panels resume normal generation. Fog accounts for a negligible portion of annual output loss — far less than cloud cover or short winter days. It is not a factor that should influence your decision to install solar.

Output in Fog vs Other Conditions

| Weather Condition | Panel Output (% of peak) | |-------------------|-------------------------| | Bright sunshine | 90–100% | | Light cloud | 50–70% | | Heavy cloud | 10–30% | | Fog | 5–15% | | Heavy rain | 5–15% | | Snow covering | 0–5% | | Night | 0% |

Fog sits at the bottom of the output range — similar to heavy rain. The difference: fog usually clears within hours (often by 10–11am), while heavy cloud can persist all day. After fog clears, panels generate normally for the rest of the day.

Annual impact of fog: UK fog occurs on 20–40 days per year (varies by location — more in valleys and coastal areas). Most fog is morning-only. The total annual output lost to fog is approximately 0.5–1% — negligible.

Source: Met Office UK fog statistics; solar output modelling.

Fog typically clears by mid-morning — panels resume normal output — Fog is a morning phenomenon — by 10-11am it typically clears and panels generate normally.

Why Fog Reduces Output

Fog is essentially a ground-level cloud — millions of tiny water droplets suspended in the air. These droplets:

1. Scatter light — reducing the intensity that reaches panel surfaces 2. Block direct sunlight — eliminating the strongest component of solar radiation 3. Allow only diffused light — weak ambient light from all directions

The light level in thick fog can be as low as 100–500 lux — compared to 100,000 lux in direct sunshine. This 200–1,000x reduction explains the 85–95% output drop.

However: Solar panels are sensitive to even low light levels. They begin generating at around 100 lux — which fog provides. The output is tiny (a few watts per panel) but not zero.

Source: Atmospheric optics; solar cell light response curves.

Solar panels still respond to diffused light in fog — minimal but present output — Even in fog, panels respond to diffused light — output is minimal but technically present.

UK Fog Patterns

Where fog is most common in the UK: - River valleys (Thames, Severn, Trent) - Coastal areas (especially east coast in spring/autumn) - Low-lying inland areas - Urban areas in winter (radiation fog from clear, cold nights)

When fog occurs: - Autumn and winter mornings (October–February peak) - Rarely persists past midday (strong sunlight burns it off) - More common in calm, clear conditions (not with wind or rain)

Seasonal impact on solar: - Fog coincides with the lowest-output months anyway (October–February) - Morning fog clearing by 10am still allows 4–6 hours of afternoon generation - The lost output from fog is within the margin of error for annual savings estimates

Bottom line: Fog is a weather condition, not a solar problem. All reputable savings estimates already account for UK weather variation including fog. It should not factor into your decision to install solar.

Source: Met Office fog frequency data; PVGIS UK weather modelling.

UK fog does not significantly affect regional solar suitability — Fog patterns vary regionally but the impact on annual solar output is negligible everywhere.

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