Inputs
Example data table
| Scenario | Panels | Method | Cleanings/Year | Labor Rate | Productivity | Distance | Estimated Annual Cost |
|---|---|---|---|---|---|---|---|
| Utility baseline | 1200 | Manual | 6 | USD 18/hr | 40 panels/hr | 20 km | USD 2,100–3,200 |
| High dust season | 2500 | Manual | 10 | USD 22/hr | 35 panels/hr | 35 km | USD 6,500–9,500 |
| Robotic option | 5000 | Robotic | 8 | USD 18/hr | 60 panels/hr | 15 km | USD 9,000–14,000 |
Formula used
1) Cleaner-hours
Cleaner-hours = (Panel Count ÷ Productivity) × Difficulty Multiplier
2) Crew duration
Crew Duration (hrs) = Cleaner-hours ÷ Crew Size
3) Cost per cleaning
Labor Cost = Cleaner-hours × Labor Rate
Travel Cost = Distance × (Round Trip? 2 : 1) × Travel Rate
Water Cost = (Panels × Liters/Panel ÷ 1000) × Water Cost per 1000 L
Subtotal = Labor + Travel + Water + Equipment + Consumables + Method Fee
Overhead = Subtotal × Overhead%
Tax = (Subtotal + Overhead) × Tax%
Total = Subtotal + Overhead + Tax + Contingency%
How to use this calculator
- Enter system size and panel count for your site.
- Select the cleaning method and annual frequency.
- Set labor rate, crew size, and productivity values.
- Adjust difficulty to match access and safety conditions.
- Add travel, water, equipment, and consumables costs.
- Apply overhead, tax, and contingency percentages.
- Press Calculate to view results above the form.
- Use CSV or PDF buttons to export a report.
Cost drivers to capture in bids
Cleaning cost is labor, plus travel, water, equipment, and consumables. This calculator separates each driver so estimators can justify pricing to owners. Include mobilization inside productivity and document permits or curfews that slow access. Use difficulty multipliers for steep roofs, trackers, fragile modules, or clearances. Cost per panel and cost per kW create benchmarks across plant sizes.
Labor planning from cleaner-hours
Cleaner-hours are computed from panel count, productivity, and difficulty. If productivity drops from 50 to 35 panels per hour, labor cost rises immediately even with the same crew size. Crew size reduces duration, not total cleaner-hours, so it improves outage windows without lowering labor spend. Track actual cleaner-hours by season to refine rates for dust, heat, and safety briefings.
Water logistics and compliance
Water demand scales with liters per panel. Multiply by local rates and add hauling, filtration, or demineralization when required by warranties. In arid sites, low-water methods may cut direct cost and downtime, but often require more passes and microfiber inventory. Record runoff rules, especially where detergents or hard water leave residue. Convert delivery charges into a cost per 1000 liters to keep bids comparable.
Manual versus robotic scenarios
Manual cleaning suits smaller arrays and irregular layouts, while robotic service can improve consistency on large, repetitive rows. Use the robotic fee to compare options per cleaning and per year, then review cost per panel as scale increases. If robotics reduce ladder work and fall exposure, lower the difficulty multiplier to reflect fewer controls and faster setup. Confirm brush type and water use align with module coatings.
Governance, reporting, and auditability
Export results to CSV for budgeting and to PDF for approvals and audits. Store assumptions for travel rate, overhead, tax, and contingency to standardize comparisons across sites. Review annual totals against production targets and O&M plans, and adjust frequency after storms, construction, or seasonal agriculture. A quarterly sensitivity check, varying productivity and cleaning frequency, gives finance teams a range for forecasts.
FAQs
Q: How do I choose a difficulty multiplier?
A: Start with 1.00 for easy access on flat ground. Use 1.25 for moderate obstructions or safety steps, and 1.50+ for steep roofs, fragile areas, or complex layouts. Calibrate using past crew hours from similar sites.
Q: What productivity value should I enter?
A: Use historical panels cleaned per hour per cleaner. If you lack data, run three test rows, time the work, and compute panels divided by hours. Reduce the value when heat, wind, or long hose runs slow movement.
Q: Does increasing crew size lower total cost?
A: Not usually. Crew size mainly reduces on-site duration because total cleaner-hours stay similar. Total cost drops only if a larger crew improves productivity, reduces overtime, or avoids additional mobilizations within a strict access window.
Q: How should I treat water truck charges?
A: Convert the delivery invoice into a cost per 1000 liters. Add any stand-by time as extra equipment or consumables. This keeps the calculator comparable across sites and makes updates easy when suppliers or routes change.
Q: When should I consider robotic cleaning?
A: Robotics can help on large, uniform arrays where repeatability matters. Compare the robotic fee against labor savings and safety benefits. Also verify compatibility with module coatings and confirm the vendor’s service level for breakdowns.
Q: What do the CSV and PDF exports include?
A: Exports capture the latest inputs and calculated results, including subtotal, overhead, tax, contingency, and annual cost. Use CSV for budget rollups and PDF for approvals or tender files. Recalculate after edits to refresh exports.