Offline
No internet, no account required.
NREL
Validated against the standard.
PDF export
Pro-only. Generate professional reports.
$2.99 Pro
Lifetime unlock. No subscriptions.
How it works
Enter your values
Type in your inputs — the app fills code tables and constants for you, so there's nothing to look up.
Get a code-checked result
Instant answer with a clear PASS / FAIL and the exact NREL reference behind every number.
Save & export
Keep a history of calculations and export a clean PDF report to share or attach to a permit (Pro).
What this calculator does
How much energy will the array actually make? This app estimates annual and monthly PV production from system size, location sun hours, tilt and orientation, and a system derate — the same logic behind tools like PVWatts, in your pocket.
How it works
Annual kWh ≈ system kW × peak sun hours × 365 × derate
Tilt and azimuth adjust the effective sun hours; a south-facing array at latitude tilt captures the most, while east or west and steep or flat angles capture somewhat less.
Worked example
A 9.4 kW array at 4.5 sun hours and a 0.80 derate: 9.4 × 4.5 × 365 × 0.80 = about 12,350 kWh/year — enough to offset a 12,000 kWh home with margin.
Related calculators
Size the system with the panel sizing calculator and value the output with the ROI calculator.
Production estimate FAQ
How accurate is the estimate?
Using realistic sun hours and a derate around 0.77 to 0.80, it lands close to detailed tools like PVWatts for a quick field estimate. Site shading and weather years cause the spread.
Do tilt and direction matter?
Yes. A south-facing array near latitude tilt produces the most; east, west, or steep angles reduce the effective sun hours, which the app adjusts for.
Monthly and annual?
Both. It estimates annual production and the monthly shape so customers can see the seasonal swing.
Does it work offline?
Yes, it runs 100% offline with no account. Free with rewarded ads; a one-time $2.99 Pro unlock adds PDF export and saved history.
Get Solar Production Estimate on your phone
Free with rewarded ads · $2.99 lifetime Pro · iOS & Android. Works 100% offline on the job site.