Solar Production Calculator
How many kWh will your solar panels produce? Enter a ZIP code and system size for an instant production estimate powered by NREL PVWatts V8. Free, no phone number, no lead capture - results stay on your device.
Your Location & System
Showing a US-average scenario. Enter a ZIP for location-specific numbers.
Default 7 kW, clamped to 1-25 kW
Default 400W
Blank = your latitude (optimal)
180 = true south
Affects airflow and temperature derate
PVWatts default 14% (inverter, wiring, soiling)
US average scenario
Static estimateEstimated Annual Production
9,198
kWh per year
Monthly Average
767
kWh / month
Capacity Factor
15.0%
of nameplate, 24/7
Per Panel
511
kWh / yr per 400W panel
Monthly Production
kWh per month
Summer months outproduce winter by roughly 2:1 in most of the US. That seasonal swing is normal and is why net-metering annual true-ups matter.
More Detail
CO2 offset and environmental equivalent
This system offsets about 3.9 tons of CO2 per year at the US grid average (0.855 lb CO2 per kWh, eGRID 2023), roughly equivalent to 0.9 cars' worth of annual tailpipe emissions.
Engineering detail
Specific yield: 1,314 kWh per kW per year (a handy cross-location comparison metric).
Panel count: 18 panels at your chosen wattage.
Average sun: 4.5 peak sun hours per day.
Static estimate: kW × peak sun hours × 365 × 0.80 performance ratio. Enter a ZIP to run the full PVWatts V8 simulation.
Estimates use NREL PVWatts V8 (or a labeled static fallback) and assume an unshaded array. Actual production varies with shading, equipment, and installation quality. This is an estimate, not a quote or guarantee.
Also Interested In
How This Solar Production Calculator Works
This tool answers one question directly: how many kWh will my solar system produce? When you enter a ZIP code, the calculator resolves your latitude and longitude, then runs the NREL PVWatts V8 simulation, the same model used for professional feasibility studies and by lending institutions' engineers. PVWatts pulls measured weather-station data for your location: the solar irradiance falling on your array (adjusted for tilt and azimuth), the ambient temperature that derates panel efficiency on hot days, and a 14% system-loss factor that covers inverter conversion losses, wiring resistance, soiling, snow, and mismatch between panels. The output is a month-by-month kilowatt-hour profile, which this page summarizes as an annual total, a capacity factor, and a per-panel figure.
If the PVWatts API is temporarily unavailable, the calculator never shows a blank or NaN result. It falls back to a clearly labeled static estimate built from your ZIP's average peak sun hours (kW × sun hours × 365 × a 0.80 performance ratio), so you always get a usable number and can see exactly which model produced it. That is the same honest-estimates approach we use across every tool on this site, and it is why we state the model, the loss factor, and the data source on the page instead of hiding them.
What a Production Estimate Does Not Tell You
Three real-world factors sit outside any simulation. Shading: a chimney, a neighbor's tree, or winter dormancy on nearby trees can cut a string's output far more than the loss factor assumes; a shade analysis is worth it if your roof has obstructions. Inverter clipping: if your inverter is undersized relative to the array, spring and fall middays will cap production even while the panels could make more. Seasonal variance: December output in northern states is roughly half of June output, and snow cover can push it lower still; annual totals smooth this out, but your monthly bill will not. Use the monthly chart above to see the swing for your location before you size a battery or a net-metering true-up expectation around summer numbers.
How Much Energy Does a Solar Panel Produce?
Per-panel output comes down to wattage times sun. A modern 400W panelproduces about 1.5 kWh per day at the US average of 4.5 peak sun hours (400W × 4.5h × 0.86 performance ratio), or roughly 500-650 kWh per year. Phoenix-area panels clear 650 kWh; Seattle-area panels sit nearer 400. Multiply by panel count and you have a quick sanity check on any installer's production estimate: a 7 kW array of 400W panels (18 panels) should produce somewhere between 9,000 and 12,500 kWh per year in most of the continental US. If a quote projects dramatically more than that, ask which model and loss factor it used.
Ready for the next step? size a system to your actual usage, project output across 25 years of degradation, or run an address-level rooftop analysis. Every tool is free, with no sign-up and no phone-number gate.
Frequently Asked Questions
How accurate is this solar production calculator?
The calculator runs NREL PVWatts V8, the same simulation engine used for professional feasibility studies. It models your location's measured irradiance, panel temperature derate, and a 14% system-loss factor covering inverter inefficiency, wiring, and soiling. Typical error versus actual first-year production is within 10-20% for an unshaded, well-installed array. When the PVWatts API is unavailable, the page falls back to a static peak-sun-hour estimate for your ZIP and clearly labels the result as an estimate.
What affects my solar production the most?
Four things dominate: shading (even partial shade on one panel can cut a string's output), orientation (azimuth 180 degrees, true south, is optimal in the US), tilt (production falls off slowly within about 15 degrees of your latitude), and system losses from soiling, snow, wiring, and inverter clipping. Seasonal variance is large and normal: June output in most of the US is roughly double December output.
Is this solar power estimator really free?
Yes, completely. No sign-up, no email gate, no phone-number capture, and no lead sales. The calculator runs in your browser and calls NREL's public PVWatts API directly. We publish tools like this because gated 'free estimate' sites charge installers $50-$300 per lead, and that cost gets built into your quote.
How much energy does a solar panel produce?
A modern 400W panel produces roughly 1.3-1.8 kWh per day, or 500-650 kWh per year, in most of the US. The math: 400W times 4.5 average peak sun hours times an 0.86 performance ratio equals about 1.5 kWh per day. Hot, sunny southwestern states reach the high end; cloudy northern states sit near the low end. The per-panel result in this calculator uses your actual ZIP and panel wattage.