1. The Basic Formula for Solar Energy Output

A widely used formula to estimate solar system output is:

Daily Energy Output (kWh) = System Size (kW) × Average Sun Hours × System Efficiency

Explanation:

• System Size (kW): The total DC capacity of the installed panels.
• Average Sun Hours: Peak sun hours per day, varies by region (e.g., 4–6 hours/day).
• System Efficiency: Includes losses due to inverter conversion, temperature, dust, shading, wiring, etc. (typically 75–85%).

Note: 

• Monthly Output (kWh) = Daily Output × 30
• Annual Output (kWh) = Monthly Output × 12

2. Key Factors Affecting Solar Power Output

Factor	Description
Location (Irradiation)	The amount of solar energy received (measured in kWh/m²/day).
System Size (kWp)	Larger systems generate more power—assuming similar sunlight and orientation.
Tilt and Orientation	South-facing (in northern hemisphere) and tilt ~30° often yield best results.
System Losses	Due to inverter efficiency, shading, dirt, cable loss, temperature derating, etc.
Module Efficiency	Higher-efficiency modules generate more power per square meter.

3. Sample Calculation: Residential 5kW System

Let's say you're in Sydney, Australia, where average sun hours ≈ 4.5 h/day. Assuming 80% system efficiency:

Step 1 – Calculate daily output:
5 kW × 4.5 sun hours × 0.80 efficiency = 18 kWh/day

Step 2 – Estimate monthly output:
18 kWh/day × 30 days = 540 kWh/month

Step 3 – Estimate annual output:
540 kWh/month × 12 months = 6,480 kWh/year

This could offset most of an average household's energy usage.

4. Comparing Power Output by Region

Here's a simplified comparison of expected daily output from a 10kW system in different cities:

Location	Avg Sun Hours	Efficiency (%)	Daily Output (kWh)
Dubai, UAE	6.5 h	80%	52.0
Los Angeles, USA	5.5 h	82%	45.1
Munich, Germany	3.2 h	78%	25.0
Nairobi, Kenya	5.7 h	81%	46.2

Peak sun hours vary with season, latitude, and weather conditions.

5. Tools & Methods for Accurate Yield Estimation

For larger or professional systems, use simulation tools like:

• PVsyst / PV*SOL: Professional-grade simulation tools for accurate system modeling.
• NREL PVWatts Calculator (USA): Free online tool using local irradiance data.
• Global Solar Atlas: Offers irradiation data and PV potential globally.
• Google Project Sunroof: Estimates solar yield for residential rooftops (select countries).

These tools consider local climate, tilt angle, shading, module degradation, and hourly solar radiation patterns.

6. Frequently Asked Questions

Q1: What's the difference between sun hours and daylight hours?
Peak sun hours refer to the number of hours per day when solar irradiance reaches 1,000 W/m². This differs from total daylight time and is a more accurate measure for system output.

Q2: Do solar panels produce the same output year-round?
No. Seasonal changes, weather, and temperature affect daily yield. Summer often produces more, winter less.

Q3: How do I know the real-world output of my installed system?
Monitoring systems (like inverter platforms or smart apps) track real-time generation and historical trends.

Q4: How much electricity does a 10kW solar system produce annually?
Depending on location, typically between 10,000–16,000 kWh per year.

Q5: How much roof space is needed for 1kW of solar panels?
Approximately 6–8 m², depending on panel efficiency.