For solar installers
Solar panel output calculator for client estimates
Enter a zip code, roof pitch, orientation and system size to get annual kWh output, bill savings and simple payback, worked from NLR (formerly NREL) PVWatts v8 data. Free, and no signup.
Using these numbers to build a proposal? See how Payaca turns production estimates into proposals, AHJ permits and PTO paperwork.
Think you can design it? Try today's Solar design of the day.
Solar yield calculator
Estimate your annual solar generation using NLR (formerly NREL) PVWatts data
Glow, limited release
Run PVWatts on the roof you're quoting
Glow runs PVWatts on the customer's real roof and puts the production estimate and the kit on the proposal.
A solar production calculator estimates the annual electricity output (kWh) of a solar panel system based on your location, roof orientation, tilt angle, system capacity (kWp), and shading conditions. In the US, a typical 6 kW residential system generates between 7,000-11,000 kWh per year depending on location, with the Southwest producing roughly 70% more energy than the Pacific Northwest. This calculator uses NLR PVWatts v8, the industry-standard solar performance model from the U.S. Department of Energy. Looking for business ROI instead? Try our ROI calculator. Running your install business on a tool that wasn't built for solar? See how Payaca compares to ServiceTitan and Jobber for clean-energy operations.
How we calculate your solar production
Our calculator uses NLR PVWatts v8, the industry-standard solar performance model developed by the National Laboratory of the Rockies (NLR, formerly NREL), part of the U.S. Department of Energy. It's the same tool used by professional solar installers to estimate system performance.
How it works: When you enter your zip code, we look up the nearest weather station from the National Solar Radiation Database (NSRDB). PVWatts uses typical meteorological year (TMY) data to model hour-by-hour solar panel performance for your specific location, tilt angle, and orientation.
Location-specific data: The model accounts for your local solar resource (global horizontal irradiance), temperature effects on panel efficiency, and system losses. A 1 kW system in Phoenix, AZ produces roughly 1,800 kWh/year compared to about 1,100 kWh/year in Seattle, WA.
Financial estimates: Savings are calculated using the EIA national average residential electricity rate (18.05 cents/kWh) for energy you use directly, plus a conservative net metering credit rate (9 cents/kWh) for surplus energy exported to the grid. Actual rates vary significantly by state and utility. Lifetime figures account for 0.5% annual panel degradation over 25 years.
Frequently asked questions
What is PVWatts?
PVWatts is a solar energy calculator developed by the National Laboratory of the Rockies (NLR), formerly the National Renewable Energy Laboratory (NREL). It estimates the energy production of grid-connected photovoltaic systems using location-specific solar resource data from the National Solar Radiation Database (NSRDB). It's the most widely used solar estimation tool in the US solar industry.
How accurate are these estimates?
PVWatts uses historical weather data from the nearest weather station and has been validated against real-world solar installations. Estimates are typically within 10-15% of actual production. Factors like local microclimate, equipment quality, inverter efficiency, and soiling can affect real-world performance.
What is net metering?
Net metering allows solar panel owners to send excess electricity back to the grid and receive credits on their utility bill. Policies vary significantly by state. Some states offer full retail rate credits, while others offer reduced rates or have transitioned to net billing (e.g. California NEM 3.0 at 3-7 cents/kWh). We use a conservative estimate of 9 cents/kWh. Check your local utility for exact rates.
Is there a federal solar tax credit?
The 30% federal residential solar tax credit (25D) expired on December 31, 2025 under the One Big Beautiful Bill Act. There is no residential solar tax credit in 2026. For commercial solar projects, the Investment Tax Credit (48/48E) is still available. Projects that began construction by July 4, 2026 keep the credit under the earlier rules; projects that begin construction after that date must be placed in service by December 31, 2027. Some state and local incentives may also be available. This calculator shows savings from electricity bill reduction and net metering only, without any tax credits factored in.
Why do results vary so much by location?
Solar irradiance varies dramatically across the US. The Southwest receives roughly 5.5-6.5 kWh/m2/day of solar radiation, while the Pacific Northwest averages 3.5-4.5 kWh/m2/day. Temperature also matters. Panels are slightly less efficient in extreme heat, which is why a cooler, sunny location can sometimes outperform expectations.
What self-consumption ratio should I use?
Self-consumption depends on your household's electricity usage patterns. A typical home without battery storage self-consumes around 30-50% of generated electricity. With a battery, this can rise to 60-80%. We default to 50% as a reasonable middle ground.