Formula Used
The calculator first finds the direct current array capacity.
DC capacity kW = number of panels × panel watts / 1000
Gross daily energy is based on local peak sun hours.
Gross daily kWh = DC capacity kW × peak sun hours
The temperature factor adjusts production when cell temperature is above or below the reference point.
Temperature factor = 1 - temperature coefficient × (cell temperature - reference temperature)
The final loss factor multiplies inverter efficiency, wiring loss, shade loss, soiling loss, availability, degradation, and temperature effect.
Net daily kWh = gross daily kWh × total loss factor
Monthly kWh = net daily kWh × days
Yearly kWh = net daily kWh × 365
Savings = energy kWh × electricity rate
CO2 saved = yearly kWh × CO2 emission factor
How to Use This Calculator
Enter the number of panels and the watt rating from the panel label.
Add average peak sun hours for your site.
Enter real losses for wiring, shade, dirt, inverter conversion, and downtime.
Use panel cell temperature when possible. It is usually higher than air temperature.
Enter your electricity rate to estimate savings.
Use a local emission factor to estimate carbon reduction.
Press Calculate. The result appears above the form and below the header.
Use CSV or PDF buttons to export the result.
Example Data Table
| Case |
Panels |
Panel W |
Sun Hours |
Total Loss |
Estimated Daily Output |
| Small rooftop |
10 |
450 W |
4.8 |
18% |
17.7 kWh |
| Home system |
20 |
550 W |
5.2 |
20% |
45.8 kWh |
| Commercial array |
80 |
600 W |
5.6 |
16% |
225.8 kWh |
Solar Planning Overview
Solar panel energy production changes through the day. It also changes across seasons. A strong calculator must include more than rated panel watts. Real systems lose energy through heat, wiring, inverter conversion, dust, shade, and downtime. This calculator joins those factors in one estimate. It helps users compare expected daily, monthly, and yearly output before buying equipment or checking an existing array.
Why Losses Matter
Panel rating is tested under standard laboratory conditions. A roof rarely matches those conditions. Hot cells reduce power. Dirt blocks light. Shade may cut production from a whole string. An inverter also uses part of the energy while changing direct current into alternating current. Small losses can combine into a large reduction. By entering each loss separately, the user can see which factor hurts output most.
Electrical Planning Benefits
Energy output is useful for several decisions. It can size battery storage. It can compare solar production with household load. It can estimate bill savings using a local electricity rate. It can also show carbon reduction with a chosen emission factor. These values support a clearer electrical design. They also help owners set realistic expectations for cloudy months and low sun periods.
Practical Use Cases
Installers can use this tool during early site screening. Students can study capacity, irradiance, and loss relationships. Homeowners can test panel counts and different inverter efficiencies. Maintenance teams can compare expected output with meter readings. If measured energy is far lower than the estimate, the site may have shade, soiling, wiring, or equipment problems.
Better Estimates
Use measured peak sun hours when possible. Use a realistic temperature value for the panel surface, not only the air. Check shading at different times of the year. Update the loss values after cleaning, repair, or design changes. The calculator gives an engineering estimate. A full project still needs local weather data, roof layout review, code checks, and professional electrical design.
Data Quality Tip
Enter values from trusted labels and local solar maps. Avoid perfect conditions unless they truly apply. Save each result before changing inputs. Comparing several cases reveals whether more panels, less shade, better cleaning, or a higher efficiency inverter gives the strongest improvement during the full operating year ahead.
FAQs
What is solar panel energy production?
It is the electrical energy a solar array can produce over a period. It is usually shown in kilowatt-hours. It depends on panel capacity, sun hours, orientation, losses, temperature, and equipment efficiency.
Why are peak sun hours important?
Peak sun hours convert changing sunlight into an equivalent number of full-power sunlight hours. Higher values increase expected daily energy. Use local monthly data for better estimates.
Does panel wattage equal real output?
No. Panel wattage is a test rating. Real output is lower or higher based on heat, irradiance, dirt, shade, wiring, inverter losses, and panel direction.
What temperature coefficient should I enter?
Use the value from the panel datasheet. Many panels lose about 0.30% to 0.45% per degree Celsius above the reference temperature.
Why include inverter efficiency?
Panels produce direct current. Most buildings use alternating current. The inverter conversion process has losses, so inverter efficiency affects final usable energy.
Can this calculator estimate bill savings?
Yes. Enter your electricity rate. The calculator multiplies produced energy by that rate. Actual savings may differ because tariffs, net metering, and fixed charges vary.
What is performance ratio?
Performance ratio shows how much gross rated production remains after practical losses. A higher ratio means the system keeps more of its theoretical energy.
Is this result suitable for final design?
It is useful for planning and comparison. Final design should also include roof layout, code rules, shading study, weather data, protection devices, and professional review.