Daily use = monthly kWh × 12 ÷ 365.
Target solar energy = daily use × desired offset ÷ 100.
Adjusted sun hours = peak sun hours × tilt factor × azimuth factor × (1 − shading loss).
Performance ratio = (1 − system losses) × inverter efficiency.
Required kW DC = target daily kWh ÷ (adjusted sun hours × performance ratio).
Panels needed = ceiling(required kW × 1000 ÷ panel wattage).
Annual production = actual kW × adjusted sun hours × performance ratio × 365.
Savings = self used kWh × retail rate + exported kWh × export credit − maintenance.
Payback = net installed cost ÷ annual net saving.
How to Use This Calculator
Enter the project address first. Add latitude and longitude if you use a map tool. Enter monthly kWh from a bill. Add local peak sun hours from a solar atlas or installer report. Set roof area, usable roof share, panel wattage, losses, shading, and inverter efficiency.
Next, enter prices, export credit, incentives, and yearly maintenance. Add battery settings if backup storage matters. Press Calculate. The result appears above the form. Use CSV for spreadsheet records. Use PDF for a simple report.
Address Based Solar Planning
A solar estimate starts with location. An address tells you where the roof sits. It also hints at climate, sunlight, utility prices, and shade risk. This calculator uses the address as the project label. Then it uses latitude, longitude, peak sun hours, and roof data to build a practical estimate. You can test a home, shop, school, farm, or small office. It is helpful for early budgets. It also supports quick site comparisons. You can change one field and see the effect. That makes planning faster and less confusing. The goal is a clear starting point before detailed design work begins with confidence.
What The Calculator Measures
The tool compares energy use with expected solar production. Monthly kWh is converted into daily and annual demand. Your target offset sets how much of that demand should be covered. Peak sun hours show the average daily solar resource. Losses, shading, inverter efficiency, tilt, and azimuth adjust the final output. Panel wattage and panel area decide the number of panels and roof space needed.
Cost, Savings, And Payback
Solar value depends on more than panel count. The calculator estimates gross system cost from dollars per watt. It subtracts incentives to show net cost. Then it compares self used solar power with exported energy. Self used power saves the retail rate. Exported power earns the credit rate. This gives a more realistic yearly saving. Payback is the net cost divided by yearly saving.
Roof And Battery Checks
A large bill does not always fit on a small roof. The roof capacity check compares usable roof area with panel area. If panels exceed the space limit, the result warns you. Battery sizing is also estimated. It uses backup load, autonomy days, depth of discharge, and battery efficiency. This helps plan backup power without oversizing storage.
Using Results Wisely
Results are estimates, not a permit design. Real projects need shade mapping, structural checks, wiring review, and local rules. Utility policies can also change savings. Use the result to compare options before calling an installer. Try different offsets, panel sizes, and cost rates. Save the report as CSV or PDF. Keep the address, assumptions, and outputs together. This makes quotes easier to compare.
FAQs
Does the address calculate sunlight automatically?
No. This version stores the address and uses entered latitude, longitude, and peak sun hours. You can add a geocoding or solar API later if you want live location data.
What are peak sun hours?
Peak sun hours show the average daily solar energy at a location. A higher value means each installed kilowatt can produce more electricity during the year.
Why does shading reduce the result?
Shade blocks sunlight and lowers panel output. Even partial shade can reduce production. Enter an estimated shading percentage to make the system size more realistic.
What is desired offset?
Desired offset is the share of your yearly electricity use you want solar to cover. A 100 percent offset targets full annual usage coverage.
How is panel count calculated?
The calculator divides required system watts by panel wattage. It rounds up to a whole panel. Then it checks if that panel count fits the usable roof area.
What is self consumption?
Self consumption is the share of solar energy used directly on site. It usually saves the full retail rate, so it often has higher value than exported energy.
Can this estimate battery size?
Yes. Enter backup load, autonomy days, usable battery depth, and battery efficiency. The tool estimates the storage capacity needed for backup planning.
Can I save the result?
Yes. Use the CSV button for spreadsheet work. Use the PDF button for a simple shareable report with inputs, outputs, and review notes.