Solar System Designer Tools
Solar Yield Calculator
Estimate how much electricity your solar panel system will produce each day and over a full year — with real-world adjustments for temperature losses, shading, and inverter efficiency.
How Solar Yield Is Calculated
Theoretical output is always higher than real-world output. The calculation applies several derating factors:
Daily Output (kWh) = Array Size (kW) × Peak Sun Hours × Performance Ratio
Performance Ratio Breakdown
- Temperature losses (4–8%): Panels lose ~0.4–0.5% efficiency per °C above 25°C. A summer day at 45°C ambient means panels hit 65°C — an 8% loss.
- Inverter efficiency (3–5%): String inverters run 95–97% efficient at optimal load.
- Wiring losses (2–3%): Resistance in cables dissipates energy as heat.
- Soiling and shading (2–5%): Dust, bird droppings, and partial shade reduce output.
- Module mismatch (1–2%): Slight differences between panels in a string reduce overall output.
A typical real-world Performance Ratio is 0.75–0.85. The calculator defaults to 0.80 (80%).
Frequently Asked Questions
How much electricity does a 5kW solar system produce per day?
A 5kW system typically generates 15–25 kWh per day depending on your location. In a sunny Southwest location with 5.5 peak sun hours and 80% performance ratio: 5 × 5.5 × 0.80 = 22 kWh/day. In a cloudy Northeast location with 3.5 PSH: 5 × 3.5 × 0.80 = 14 kWh/day.
How does temperature affect solar panel output?
Most silicon solar panels have a temperature coefficient of -0.40% to -0.50% per °C. When panels heat up above 25°C (their standard test temperature), output drops. A panel at 65°C surface temperature loses (65-25) × 0.45% = 18% of its rated output. This is why cooler climates often see better per-panel performance than hot deserts despite having fewer sun hours.
What is solar panel degradation and how does it affect yield over time?
Solar panels lose about 0.5–0.7% of their output capacity per year (premium panels guarantee ≤0.5%/year). After 25 years, a panel rated at 400W will produce roughly 350–380W. Plan your system to still meet your energy needs at year 25, not just year 1.
Does panel orientation affect yield in the southern hemisphere?
Yes — in the southern hemisphere, panels should face north (not south) for maximum yield, as the sun passes to the north. Everything else about the calculation remains the same; only the optimal orientation direction changes.