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.