Share this page
Copy the link or send it to your audience.
Point your camera at the QR code to open this page on any device.
Solar Panel Calculator
Size a solar array to cover your electricity usage.
Panels = daily kWh × 1000 / (panel W × sun hours × efficiency). A 10 kWh/day home in 4.5 sun hours with 400 W panels needs about 7 panels.
How it works
Panels = daily kWh × 1000 / (panel W × sun hours × efficiency). A 10 kWh/day home in 4.5 sun hours with 400 W panels needs about 7 panels.
Worked example
10,000 Wh ÷ (400 W × 4.5 h × 0.8) = 10,000 ÷ 1,440 ≈ 7 panels.
Recommendations
- Add a 10–20% margin for cloudy days
- Orient panels south (north in the southern hemisphere)
- Check your roof angle and shading first
Tips & advice
- Get your actual bill to read real consumption
- A 400 W panel needs about 2 m² of roof
- Clean panels a few times a year
Fuel Consumption Calculator
Find your real fuel consumption from a full tank test.
Fuel Cost Calculator
Know the cost of your trip before you leave.
Weeks Between Dates Calculator
Find out exactly how many weeks separate two dates.
Months Between Dates Calculator
Know how many months separate any two dates.
Solar Panel Calculator
Size a solar array to cover your electricity usage.
Use the calculatorInvoice Generator FAQs
Yes, all 20 home calculators are 100% free, private and run entirely in your browser. No account needed.
They use standard industry formulas. Always round up for materials and confirm with a professional for structural work.
The calculators use metric units (meters, liters, m³). Convert imperial measurements beforehand if needed.
No. Calculations happen instantly in your browser and nothing is sent to any server.
More Free Tools
Explore the whole collection — no signup, 100% free & private.