Photovoltaic (PV) Solar Yield Calculator
Estimate your solar energy production and potential savings based on system specifications.
How to Calculate Photovoltaic Solar Yield
Understanding the output of a solar PV system is critical for determining the return on investment. The core formula for calculating the daily energy yield (E) in kilowatt-hours (kWh) is:
E = P × H × f
- P (System Capacity): The peak power rating of your solar array in kilowatts (kWp).
- H (Peak Sun Hours): This is not just daylight hours, but the equivalent number of hours per day when solar irradiance averages 1,000 W/m². This varies significantly by geography.
- f (Efficiency Factor): No system is 100% efficient. We must account for losses due to inverter conversion, wiring resistance, dust on panels, and temperature fluctuations (usually 0.75 to 0.85).
Understanding Peak Sun Hours
A location might have 12 hours of daylight, but only 4 to 6 "Peak Sun Hours." For example, areas in the Southwestern United States often see 6+ hours, while Northern Europe might average 2.5 to 3 hours daily across the year. Using an annual average helps normalize the difference between summer peaks and winter troughs.
Financial Impact and ROI
The financial benefit is calculated by multiplying the annual kWh production by your local utility's electricity rate. If you spend $15,000 on a system that saves you $1,500 a year in electricity costs, your "simple payback period" is 10 years. This calculation ignores incentives like tax credits or SRECs, which can often reduce the payback period by 30% or more.
Example Calculation
Let's look at a typical residential setup:
- System Size: 6 kWp
- Location: Average (4.5 Peak Sun Hours)
- Efficiency: 80% (0.80)
- Logic: 6 kWp × 4.5 hours × 0.80 = 21.6 kWh per day.
- Monthly: 21.6 kWh × 30 days = 648 kWh per month.