How Much Are Your Dirty Solar Panels Costing You Per Month?
Calculate the monthly cost of skipping solar panel cleaning — with real San Diego numbers.
Dirty solar panels in San Diego typically lose 15–25% of production. On a 7kW system at SDG&E rates, that's $30–$60 per month evaporating from your savings — money you've already paid for in your system loan or PPA.
The math: production loss × your kWh rate
A 7kW San Diego system produces roughly 950 kWh per month. A 20% soiling loss is 190 kWh — at SDG&E's effective on-peak rate of $0.45–$0.55/kWh under TOU-DR1, that's $85–$105 in lost offset every billing cycle. Even at the conservative blended rate of $0.32, you're losing $60 per month.
Why the number gets worse over time
Soiling compounds. Dust binds with pollen, bird droppings bake on in 100°F summer panel temperatures, and what would have rinsed off in March is permanent by September. Systems that haven't been cleaned in 18+ months routinely measure 25–35% below design production.
What a cleaning typically recovers
A first-time Saturn cleaning on a neglected San Diego system recovers 15–22% of production on average — measurable in your monitoring app within the first sunny week. The cleaning pays for itself in 4–8 weeks, and a biannual plan keeps you near peak the rest of the year.