What are peak sun hours?

Peak sun hours (PSH) represent the number of hours per day when sunlight intensity averages 1,000 W/m², which is the standard test condition for solar panels. A location with 5 PSH means the sun delivers the equivalent of 5 full hours of peak irradiance per day. This is not the same as daylight hours. Most US locations range from 3.5 to 6 PSH.

What efficiency percentage should I use?

A real-world solar system loses energy through inverter conversion (typically 4–6%), wiring resistance (1–3%), temperature de-rating (5–10%), and occasional shading or soiling (1–5%). A default of 80% is a conservative but realistic estimate. Well-maintained systems in mild climates can reach 85–90%.

How is daily output calculated?

Daily output (kWh) = (Panel Wattage × Number of Panels × Peak Sun Hours × Efficiency) / 1000. For example, 10 panels at 400 W each, 5 peak sun hours, and 80% efficiency gives (400 × 10 × 5 × 0.80) / 1000 = 16 kWh per day.

Why does actual output differ from this estimate?

This tool uses average peak sun hours. Actual output varies day to day due to cloud cover, seasonal sun angle changes, panel degradation over time (typically 0.5% per year), and local obstructions. Treat the result as a long-run average, not a guaranteed daily figure.

Can I use this for commercial or utility-scale arrays?

Yes. Simply enter the panel wattage and total panel count for your array. For very large systems, note that utility-scale installations often achieve higher efficiencies due to optimized tracking mounts and commercial inverters.

Solar Panel Output Calculator

Enter your panel wattage, panel count, peak sun hours, and system efficiency to instantly calculate daily and annual solar energy output in kWh.

Array Parameters

Panel Wattage (W)

Rated power of one panel under standard test conditions

Number of Panels

Total panels in your array

Peak Sun Hours per Day (h)

Average hours of full-intensity sunlight (1,000 W/m²) per day

System Efficiency (%)

Accounts for inverter, wiring, temperature, and shading losses

Energy Output

Array Capacity

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Daily Output

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kWh / day

Monthly Output

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kWh / month

Annual Output

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kWh / year

Calculation Breakdown

Results will appear after you calculate.

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Summary

This solar panel output calculator estimates how much electricity your solar array will produce each day and over a full year. Enter the wattage of each panel, the total number of panels, average peak sun hours for your location, and a system efficiency factor to account for real-world losses from inverter conversion, wiring resistance, shading, and temperature. All calculations happen instantly in your browser with no data sent to any server.

How it works

Enter the rated wattage of a single solar panel (e.g., 400 W).
Enter the total number of panels in your array.
Set the average peak sun hours per day for your location (typically 3–6 hours).
Adjust the system efficiency percentage to account for inverter, wiring, shading, and temperature losses (default 80%).
The calculator instantly computes total array capacity, daily output, monthly output, and annual output in kWh.

Use cases

Homeowners checking whether their rooftop array will cover their electricity bill.
Engineers sizing a solar installation before purchasing equipment.
Off-grid system designers verifying battery charging capacity.
Students studying photovoltaic system design and energy yield.
Real estate professionals estimating solar production for listings.
Agricultural operations calculating output for irrigation pump power.
DIY solar installers comparing panel configurations before finalizing a design.

Frequently Asked Questions

Last updated: 2026-05-29 · Reviewed by Nham Vu