Pvwatts Calculator
Estimate the energy production and cost savings of a grid-connected photovoltaic (PV) system. Input your location, system size, and other parameters to get annual kWh output, savings, and payback period.
Published by:
isCalculator Editorial Team
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How to Use the PVWatts Calculator
- Enter Location – Type a city and state/country (e.g., “Los Angeles, CA”). The calculator uses a simplified sun-hours model based on known locations (e.g., LA gets ~6 hours, New York ~4.5).
- Set System Size – Input your solar array’s DC capacity in kilowatts (kW). Must be a positive number (e.g., 5 for a 5 kW system).
- Choose Module Type – Select from Standard (15% efficiency), Premium (19%), or Thin Film (10%). This adjusts the efficiency factor.
- Adjust Tilt & Azimuth – Tilt (0–90°) defaults to 20°, Azimuth (0–360° from north) defaults to 180° (south-facing). These affect energy output via simple correction factors.
- Input Electricity Rate & System Cost – Rate in $/kWh (e.g., 0.12). Cost is the total installed price in dollars (optional for payback calculation).
- Click “Calculate” – Results show annual energy (kWh), annual savings ($), and payback period (years). The formula uses: Energy = System Size × Sun Hours × 365 × Efficiency × (1 – Losses) × Tilt Factor × Azimuth Factor.
Note: This is a simplified model. For precise estimates, use the official NREL PVWatts tool.
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Frequently Asked Questions
A PVWatts calculator estimates the energy production and cost savings of a grid-connected photovoltaic system based on location, system size, and other parameters.
This calculator provides a simplified estimate. For precise results, use the official NREL PVWatts tool. Our model uses average sun hours and simplified factors.
You need your location, system size in kW, module type, tilt angle, azimuth, electricity rate, and system cost. Default values are provided.