Construction & electrical
Solar Panel Calculator
Estimate required solar system size, panel count, roof area, and expected generation from energy usage and local sun hours.
Interactive calculator
Size a solar panel system from energy usage
Estimate required solar capacity, panel count, roof area, and expected generation using monthly energy usage, sun hours, and panel specs.
Results
Required system
6.79 kW
Panel count
16
Roof area needed
33.6 m2
Estimated generation
955 kWh/mo
31.8 kWh/day
How to use it
- 01Enter monthly electricity usage in kWh and local peak sun hours per day.
- 02Add the panel wattage, panel footprint area, and an estimated system-loss percentage.
- 03Review the estimated system size, panel count, roof area, and generation output.
Result guide
- Required system size is the rough solar capacity needed to match the selected electricity use.
- Panel count rounds the system requirement up to whole panels for real installation planning.
- Roof area helps judge whether the estimate is physically realistic on the available roof surface.
About this calculator
Solar users usually want to connect electricity usage to a system size they can actually imagine, which is why panel count and roof area matter alongside total kilowatts.
A production-friendly solar calculator should include system losses, because inverter losses, temperature, wiring, and shading all reduce real-world output below the ideal panel nameplate rating.
Frequently asked questions
Why include system losses?
Because real solar systems lose some output to inverter efficiency, wiring, temperature, dirt, and other installation factors.
What are peak sun hours?
Peak sun hours represent the equivalent number of full-sun hours per day used in solar production estimates.
Does this replace a professional site assessment?
No. It is an early planning estimate, not a substitute for shade analysis, structural review, or installer design work.
Method and limitations
This calculator uses the formula and assumptions described on this page. We do not claim independent professional review. Direct references will be listed here when they support a specific rule or data source used by this calculator.
Results are estimates for general information. Verify current rules and assumptions before making financial, tax, or health decisions.
Read our Editorial and Verification Policy →Related calculators
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