Your Solar Soiling Report

📱 Your report works right here on your phone. For the full interactive map, open this page on a computer.

Should you pay for a cleaning?

Almost certainly not.

Of the 1,865 households we mapped, none would get back what a wash costs. Rain here rinses an array clean about 27 times a year for free, so one paid wash buys roughly two weeks of clean glass out of twelve months. It recovers about 4.5% of what a year of dirt costs you.

That covers the dirt rain washes off, which is the only kind we can measure. Panels also pick up a film that rain leaves behind and only a wash removes. We do not know how fast that builds up in Santa Cruz, so we count it as zero. A roof would have to be losing about another 5% of its output to that film before a $90 wash paid for itself, or under 2% for a household still on a legacy retail-credit plan.

We assumed 90% until we measured it. How we got that wrong →

Want your exact numbers? Open the calculator → Put in your own system size, electricity rate, and conditions.

Loading array data…

Each dot is one household. Zoom in to see the panels themselves.

Every property we mapped, biggest annual cost first. The spread is almost entirely system size, which we measure directly off the photograph. This is not a ranking of which roofs are dirtiest: we measured ours and it does not separate one roof from another inside a county.

The top of this list is commercial rather than residential: — of the — properties are over 20 kW and — are over 100 kW, which is a warehouse roof and not a house.

Only what is in the current map view

#	Cost of dirt / yr	System size	Panel groups