There is no single right answer, and anyone who quotes you one wash a year sight-unseen is guessing. The cadence that pays for itself depends on the site’s soiling rate, and in the Southeast that rate is driven by four things.
1. Pollen season
From late March into May, pine and oak pollen coats everything in the Coastal Plain and Piedmont. On a fixed-tilt array the film builds fastest on the lower rows and on modules with a shallow tilt. A wash timed for the end of pollen season is the single most valuable cycle most sites run.
2. Agricultural drift
Many utility-scale sites in NC, SC and VA sit next to working farmland. Tillage, harvest dust and spray drift add a second soiling peak in late summer and early fall. Sites bordered by row crops often justify a second scheduled wash.
3. Storm fallout
Tropical systems and summer thunderstorms leave debris, bird activity and mud splash on the low rows. These are condition-driven washes: you don’t schedule them, you mobilize when the site tells you to.
4. Post-vegetation residue
Mowing and herbicide cycles leave clippings and dust on adjacent rows. Sequencing the wash a few days after the vegetation pass cleans up both in one closeout — and is the reason we run both scopes with the same crew.
A working baseline
- Scheduled: one to two washes a year (post-pollen, and post-harvest where ag drift is a factor), or a quarterly program on contracts that require it.
- Condition-driven: after storm events, visible soiling, or a production drop your monitoring flags.
- Always: before/after photo evidence and a closeout report, so the wash shows up in the data and in the record.
If you want a cadence recommendation for a specific site, send us the location, array type and what your monitoring has been showing. Request a quote →