Solar kWh Estimator Inputs
Formula Used
Array Size = (Panel Wattage × Panel Count) ÷ 1000
Factor = Base System Efficiency × Inverter Efficiency × Availability × (1 − Shading Loss) × (1 − Soiling Loss) × (1 − Temperature Loss) × (1 − Wiring Loss)
Daily Energy = Array Size × Sun Hours × Combined Delivered Energy Factor
Monthly Energy = Daily Energy × Billing Days
Yearly Energy = Daily Energy × 365
Monthly Savings = Monthly Energy × Electricity Rate
Yearly Savings = Yearly Energy × Electricity Rate
Specific Yield = Yearly Energy ÷ Array Size
This method gives a more realistic estimate than a simple wattage times sun-hours approach because it accounts for multiple operational losses.
How to Use This Calculator
- Enter the wattage of one solar panel.
- Enter the total number of panels in the array.
- Add your site’s average daily sun hours.
- Set the billing period days for the monthly estimate.
- Enter system efficiency and each loss percentage realistically.
- Add inverter efficiency and system availability.
- Enter your electricity rate to estimate savings.
- Optionally adjust the CO2 factor for environmental reporting.
- Click the estimate button to view production, savings, and yield.
- Use the CSV and PDF buttons to export the output.
Example Data Table
| Scenario | Array Size | Sun Hours | Combined Factor | Daily kWh | Monthly kWh |
|---|---|---|---|---|---|
| Small Home System | 3.60 kW | 5.0 | 0.78 | 14.04 | 421.20 |
| Medium Roof System | 5.40 kW | 5.5 | 0.75 | 22.28 | 668.40 |
| Large Residential System | 8.10 kW | 5.8 | 0.77 | 36.16 | 1084.80 |
FAQs
1) What does this solar kWh estimator calculate?
It estimates solar energy output after system efficiency and loss assumptions. It also shows monthly and yearly generation, savings, specific yield, daily output per panel, and annual carbon offset.
2) Why are there separate loss inputs?
Separate loss fields let you model shading, dust, heat, wiring, inverter conversion, and uptime more realistically. That usually produces better planning estimates than one generic derate value.
3) What are sun hours?
Sun hours are the average equivalent full-power solar hours received each day. They are not the same as daylight hours. Better site data gives better production estimates.
4) What is performance ratio?
Performance ratio compares delivered energy against ideal energy before losses. A higher value means the system keeps more of its theoretical production after real-world operating reductions.
5) Can I use this for off-grid systems?
Yes, but this version focuses on production and savings estimates. For off-grid design, you would also want battery sizing, autonomy days, inverter surge limits, and load timing.
6) How accurate are the savings results?
Savings depend on the electricity rate you enter. Actual bill reduction may differ if your utility uses tiered pricing, time-of-use billing, demand charges, or export credits.
7) What is specific yield?
Specific yield shows yearly energy produced per installed kilowatt. It helps compare system quality and solar resource strength across different array sizes and installation locations.
8) Why does the graph show seasonal monthly values?
The chart turns your average daily estimate into a seasonal monthly profile for easier planning. It helps visualize how output can vary through the year even with fixed equipment.