Is Solar Panel Cleaning Worth It?

By James Stanley | Home Projects Puzzles Notes Date: Tuesday, 21 July 2026 | Category: #science

I own a modest solar array that has become visibly coated in dust. It has been at least a year since they were last cleaned—and likely two, as there was little incentive to scrub them right before selling the house.

Executive Summary: I estimate that cleaning my panels resulted in a power output boost of roughly $2\% \text{ to } 5\%$ . This translates to an annual gain of approximately £60–£150, though this benefit will diminish toward zero over the next few years as dust accumulates again.

🛠 Methodology

My setup consists of 16 panels divided into two separate banks of 8. Because the inverter tracks the output of each bank independently, I designed an experiment to isolate the effect of cleaning.

Experimental Logic

To avoid "noise" from variables like shifting cloud cover or the angle of the sun, I didn't look at raw wattage. Instead, I monitored the ratio of power between the two banks.

The Process

Establish baseline power ratio.
Clean panels in Bank A one by one.
Record readings between each panel.
Final reading after full bank is cleaned.

Note on Condition: The panels were "visibly dusty" but not caked in grime. If your panels are significantly filthier than mine, your percentage gains will likely be higher.

Panel Comparison

📊 Results & Observations

The data showed a stable initial ratio, followed by some erratic behavior during the cleaning process.

Stage	Observation	Power Ratio Effect
Baseline	Both banks dusty	Stable
Initial Wash	First panel cleaned	Unexpected significant drop
Progressive	More panels cleaned	Steady increase (as expected)
Completion	All Bank A panels clean	Ratio dropped again while idle

The "Frosted Glass" Mystery

I noticed that once the cleaning was finished, the ratio dipped again. I suspect this is due to evaporation. When the glass is wet, it is clear; as it dries, it may become slightly opaque—similar to the frosted glass effect. This leads me to wonder if polishing is required for maximum efficiency.

Data Log Snippet:

Reading 1: Baseline (0% washed) -> Ratio X
Reading 2: Partial (50% of 1 panel) -> Ratio X - Delta (Unexpected)
Reading 3: Progressive (1-8 panels) -> Ratio X + Delta (Expected)
Reading 4: Final (Dry) -> Ratio X + Delta - Small Drop

⚡ The "Tingle" Incident

While cleaning, I experienced a strange tingling sensation in my finger.

~~I initially assumed I had a tiny thistle splinter in my skin.~~ While there was a puncture mark from a thistle, the sensation persisted even after the splinter was gone. I believe the electricity was actually flowing through the point where the skin had already been breached.

According to ChatGPT, this is likely just a minor capacitive leakage common in transformerless inverters. I've decided it's not a cause for alarm.

📈 The Upgrade Dilemma

My system is roughly 15 years old, with a peak output of 3.7 kW across 16 panels. I considered whether a full hardware upgrade makes sense.

The Math

If I replaced the old panels with modern equivalents, the output would increase by $\approx 60\%$ .

Estimated Cost: £5,000
Payback Period: $\approx 3 \text{ years}$

At first glance, this seems like a "no-brainer." However, there is a massive financial catch: the Feed-in Tariff (FiT).

The Conflict:

Old System: I am paid an incredibly high rate based on total generation (not just what I export to the grid). I get paid for electricity I use myself.
New Capacity: Any additional power generated by new panels would not be covered by the old FiT. It would be subject to current tariffs, which are roughly $4\times$ worse.

Conclusion: The very incentives that made solar attractive 15 years ago now act as a financial barrier to upgrading the equipment today.

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