Performance and output

Dust and soiling loss estimator

Enter your local rainfall, dust source, tilt angle, and cleaning schedule. Get an annual kWh and dollar loss estimate from dust and general soiling.

Your system and environment

1 Project details Optional
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2 Your system
Use your system's rated annual output assuming clean panels.
Find this on a recent utility bill.
3 Your environment
Regular rain washes dust and pollen off naturally. Check NOAA climate normals for your area.
Farmland, unpaved roads, and construction sites raise particulate levels significantly.
Steeper tilt lets rain rinse dust off more effectively.
Regular cleaning removes buildup that rain alone can't fully clear.

How it works

Four steps to a soiling loss number

Step 1

Check your local rainfall

Regular rain is the biggest natural factor limiting soiling loss. Areas with under 15 inches of annual rainfall see meaningfully more buildup than areas with 30 inches or more.

Step 2

Identify your dust source

Nearby farmland, unpaved roads, or construction sites raise particulate levels well above a typical suburban baseline. If you're near a desert region, also check the desert heat impact calculator for the separate temperature effect.

Step 3

Note your tilt angle

A steeper array lets rain rinse dust and pollen off more completely than a flatter one, where debris tends to settle and stay. Check the tilt angle comparison tool if you're weighing a mounting angle decision. A yearly inspection catches that loss early, and the annual inspection cost estimator prices it.

Step 4

Decide on a cleaning schedule

Weigh the recovered output against the cost of professional cleaning, especially in low-rainfall or high-dust regions where rain alone won't keep panels clear.

Understanding your dust and soiling loss

Why rainfall does most of the cleaning for you

A system with 30 inches of annual rainfall, moderate dust exposure, and no cleaning loses around 1.7% of annual output to soiling. An 11,000 kWh/year system loses roughly 183 kWh a year under those conditions. In most climates with regular rainfall, natural rinsing keeps this loss modest without any manual intervention. A DOE assessment of 75 federal PV systems identifies soiling as one of the measurable losses that current performance models often exclude by default, which is why it shows up as underperformance if left unaddressed.

Where soiling losses get serious

Desert regions with low rainfall, areas near unpaved roads or agricultural fields, and locations downwind of construction sites tend to see the highest soiling losses, sometimes reaching 10% or more without regular cleaning. The EPA's own overview of agricultural air quality lists vehicles on unpaved roads and general materials handling among the most common sources of the coarse airborne particles that end up settling on rooftops and panels in these areas. Combine dry conditions with a flat tilt angle and the loss compounds further, since neither rain nor gravity does much work clearing the surface.

When professional cleaning pays for itself

It depends on your dust exposure and rainfall. In a low-rainfall, high-dust area, quarterly cleaning can recover enough output to pay for itself, while a system in a rainy, low-dust climate usually doesn't need it at all. Run this calculator with and without a cleaning schedule applied to compare the recovered kWh against a local cleaning service quote. A steeper array can also lean on gravity to shed dust faster between cleanings, which the array tilt angle optimizer can help you weigh against the other tradeoffs of a steeper mounting angle.

Soiling versus other output-limiting factors

Dust and soiling loss is separate from the heat-related loss covered in the hot climate efficiency loss calculator, though dry, dusty regions often see both effects at once. The humidity impact calculator covers a different climate factor that can work in the opposite direction.

What to do with this number next

Compare your soiling estimate against the real world vs nameplate output gap calculator to see how much of your total output gap this single factor accounts for.

Questions

Frequently asked

A system with 30 inches of annual rainfall, moderate dust exposure, and no cleaning loses around 1.7% of annual output to soiling. An 11,000 kWh/year system loses roughly 183 kWh a year under those conditions.

In most climates with regular rainfall, yes. Rain washes away loose dust and pollen effectively enough that manual cleaning adds little extra output for most homeowners outside of dry, dusty, or high-pollution regions.

Desert regions with low rainfall, areas near unpaved roads or agricultural fields, and locations downwind of construction sites tend to see the highest soiling losses, sometimes reaching 10% or more without regular cleaning.

It depends on your dust exposure and rainfall. In a low-rainfall, high-dust area, quarterly cleaning can recover enough output to pay for itself, while a system in a rainy, low-dust climate usually doesn't need it at all.

Related tools

Keep exploring your output

Desert heat impact on output Humidity impact on output Hot climate efficiency loss Tilt angle output comparison Real world vs nameplate output gap Shading loss estimator Cloud cover output reduction All performance and output tools