Peak Sun Hours Calculator

Calculator Inputs

Three columns on large screens, two on tablets, and one on mobile.

Calculation Mode

Daily Solar Irradiation (kWh/m²/day)

Reference Peak Irradiance (W/m²)

Daily Energy Output (kWh/day)

System Size (kW)

Performance Ratio

Array Area (m²)

Module Efficiency (%)

Balance Efficiency (%)

Soiling Loss (%)

Shading Loss (%)

Temperature Loss (%)

Wiring Loss (%)

Mismatch Loss (%)

Inverter Loss (%)

Availability Loss (%)

Tilt Adjustment (%)

Days in Period

Panel Count

Panel Rating (W)

Example Data Table

Month	Daily Irradiation	System Size	Performance Ratio	Estimated Peak Sun Hours
January	4.3 kWh/m²/day	5.04 kW	0.79	4.30 h
April	6.1 kWh/m²/day	5.04 kW	0.81	6.10 h
July	5.4 kWh/m²/day	5.04 kW	0.76	5.40 h
October	5.0 kWh/m²/day	5.04 kW	0.80	5.00 h

Formula Used

Peak sun hours express daily solar energy as equivalent hours at 1,000 watts per square meter. It converts changing irradiance into one planning value.

Primary formula: Peak Sun Hours = Daily Solar Irradiation ÷ 1 kW/m²

Energy method: Peak Sun Hours = Daily Energy Output ÷ (System Size × Performance Ratio)

Area method: Peak Sun Hours = Daily Energy Output ÷ (Array Area × Effective Efficiency)

The calculator also applies combined loss factors and optional tilt adjustment. This creates an adjusted field estimate beyond the simple theoretical value.

How to Use This Calculator

Select the calculation mode that matches your available project data.
Enter irradiation, output, or module values in the relevant fields.
Add system losses for soiling, shading, temperature, mismatch, wiring, inverter, and availability.
Use tilt adjustment if the array angle improves or reduces effective capture.
Click the calculate button to show the result above the form.
Export the result to CSV or PDF for reports, reviews, or client files.

FAQs

1. What are peak sun hours?

Peak sun hours convert daily solar irradiation into equivalent hours at 1,000 W/m². They simplify solar resource comparison across sites, seasons, and designs.

2. Is peak sun hours the same as daylight hours?

No. Daylight includes low morning and evening light. Peak sun hours measure total energy as full-strength sun equivalents, which is more useful for photovoltaic planning.

3. Why include losses in the calculation?

Real systems lose energy from dust, shading, heat, wiring, and inverter conversion. Including losses produces a more realistic performance estimate for engineering decisions.

4. Which method should I choose?

Use irradiation mode when resource data is available. Use energy mode for operating systems. Use module mode when you know array area and efficiency.

5. What is a good peak sun hour value?

It depends on site climate and season. Many locations range from about 3 to 7 peak sun hours daily, but local meteorological data is best.

6. Can this calculator size a solar system fully?

It supports early sizing and performance review. Final system design should also consider battery goals, load profile, code rules, and equipment specifications.

7. Why does my adjusted result look much lower?

High loss inputs or negative tilt adjustments reduce the theoretical value. Review each percentage carefully to confirm they reflect realistic field conditions.