Estimate whether solar panel cleaning is worth the cost using your yearly solar output, dirt loss, cleaning price, and power value.
Table of contents
How to use our Solar Panel Cleaning Payback Calculator
- Enter Clean yearly solar output using the yearly kWh your system would make with clean panels.
- Enter Power lost to dirt before cleaning as the estimated percent loss right before a cleaning visit.
- Add Cleaning cost per visit, choose Cleanings per year, and enter Electricity price for power used at home.
- Open Advanced options if some solar power is exported, then enter Clean solar power used at home and Solar export credit.
- Check Yearly gain after cleaning cost first, then compare Dirt loss needed to break even with your real dirt level to see if the result seems realistic.
Definitions
kWh: Kilowatt-hour, a unit of electrical energy. Solar apps and electric bills often use kWh to show energy made or used [1].
Clean yearly solar output: The kWh your system would make in one year if the panels were clean.
Power lost to dirt before cleaning: The estimated percent of solar output lost right before panels are cleaned.
Clean solar power used at home: The share of solar energy that reduces power you would otherwise buy from the utility.
Solar export credit: The $ per kWh credit for solar power sent to the grid.
Blended power value used: The average $ per kWh value after mixing home-used solar power and exported solar power.
Dirt loss needed to break even: The pre-cleaning dirt loss percent that would make recovered solar value equal yearly cleaning cost.
Common mistakes and quick fixes
Mistake: Using a monthly number for Clean yearly solar output.
Fix: Enter the full-year clean-panel kWh, not one bill period or one sunny month.
Mistake: Entering Power lost to dirt before cleaning as a decimal, such as 0.06 for 6 percent.
Fix: Enter 6 for 6 percent because the calculator converts percent to a decimal.
Mistake: Putting the total yearly bill in Cleaning cost per visit.
Fix: Enter the price for one visit, then use Cleanings per year to set the yearly schedule.
Mistake: Using Electricity price for power used at home for every recovered kWh when much of your solar is exported.
Fix: Set Clean solar power used at home and Solar export credit so Blended power value used matches your billing setup.
Mistake: Treating a negative Yearly gain after cleaning cost as an error.
Fix: A negative value is allowed and means the cleaning plan costs more than the recovered solar power is worth.
Limitations & Key Assumptions / Boundary Conditions
- The calculator assumes dirt loss builds evenly from 0 percent just after cleaning to the entered Power lost to dirt before cleaning before the next cleaning.
- Clean yearly solar output must already reflect your system size, location, shade, weather, inverter limits, and normal solar losses.
- Rain, pollen, dust storms, roof angle, bird droppings, snow, and nearby trees can make real soiling uneven through the year.
- The model uses one yearly average Electricity price for power used at home and one Solar export credit. Time-of-use rates and monthly minimum charges can change the real value.
- Cleaning cost savings from DIY work, safety gear, roof access, damage risk, and warranty rules are not priced unless you include them in Cleaning cost per visit.
- Payback time is not available when the recovered solar value is zero, because there is no recovered dollar value to pay back the cost.
Methodology
How the calculator values recovered solar power
The calculator first finds an average value for one recovered kWh. If all recovered solar power is used at home, this value equals Electricity price for power used at home. If some recovered power is exported, the exported share uses Solar export credit.
blended_power_value = (home_use_percent / 100 * home_electricity_rate) + ((1 - home_use_percent / 100) * export_credit_rate)
How recovered energy is estimated
The calculator uses Clean yearly solar output and Power lost to dirt before cleaning. It divides the entered dirt loss by 2 because the model assumes dirt builds evenly after cleaning, so the average loss over the cleaning cycle is half the loss right before cleaning.
annual_solar_energy_recovered = clean_yearly_output_kwh * (dirt_loss_before_cleaning_percent / 100) / 2
annual_energy_value_recovered = annual_solar_energy_recovered * blended_power_value
How cost, gain, payback, and break-even loss are found
annual_cleaning_cost = cleaning_cost_per_visit * cleanings_per_year
annual_net_gain = annual_energy_value_recovered - annual_cleaning_cost
payback_months = annual_cleaning_cost / annual_energy_value_recovered * 12
break_even_dirt_loss_percent = (2 * annual_cleaning_cost) / (clean_yearly_output_kwh * blended_power_value) * 100
Annual net gain is signed. A negative value means the yearly cleaning cost is higher than the estimated value of recovered solar power. If annual recovered value is 0 or less, payback time is shown as N/A.
Mini-example
Suppose Clean yearly solar output is 9000 kWh, Power lost to dirt before cleaning is 6 percent, Cleaning cost per visit is $150, Cleanings per year is 1, and Electricity price for power used at home is $0.17 per kWh. With 100 percent home use, Blended power value used is $0.17 per kWh. Recovered energy is 9000 * 0.06 / 2 = 270 kWh per year. Recovered value is 270 * $0.17 = $45.90 per year. Yearly gain after cleaning cost is $45.90 - $150 = -$104.10, so this plan does not pay for itself under those inputs.