Solar Panel Output Calculator
Estimate daily array energy from DC nameplate kWp (or panel watts × count), peak sun hours, and an optional overall performance factor. For planning — not a substitute for a full PV model.
Total DC nameplate power in kilowatts peak (STC sum of modules). Leave empty to use panel watts × number of panels below.
Or enter per-panel STC power and panel count
Watt rating printed on the module (often 400–550 W for residential).
How many identical modules in the string/array for this estimate.
Equivalent hours at 1 kW/m² — typical roughly 3–6 depending on site and season; use a local annual average for a single number.
Optional “catch-all” for inverter, wiring, tilt/azimuth, temperature, soiling, and mismatch. Many well-built systems land around 75–85%. Blank = 100%.
Table of Contents
What this calculator estimates
Photovoltaic arrays are quoted in kilowatts peak (kWp) under standard test conditions (STC). Real energy per day depends on how much sun you get and how efficiently the system converts that into AC energy at your meter.
Peak sun hours summarize your site’s daily sunshine as “how many hours per day a 1 kWp array would ideally produce 1 kWh per kWp” before system losses — a handy shortcut for back-of-envelope yield.
Multiplying kWp by peak sun hours gives a first-pass daily DC energy idea; the optional performance percentage folds inverter conversion, wiring, module temperature, orientation, shading, and dirt into one number so you can match contractor assumptions or pro tools.
Use the result for budgeting, comparing quotes, or sanity-checking bills — not for warranty claims, feed-in forecasts, or financial models that require shading study and hour-by-hour simulation.
Formula
Simple daily energy model
kWh/day ≈ kWp × peak sun hours × (system performance % ÷ 100)
kWp is the sum of module STC ratings (or your single kWp field). Peak sun hours is a daily average for your choice of period (often a year).
From panel count
kWp = (W_per_panel × panel_count) ÷ 1,000 — then use the same daily formula
Example: 16 × 400 W = 6.4 kWp. At 4.5 h and 80% → 6.4 × 4.5 × 0.8 ≈ 23.0 kWh/day.
Quick Reference
| kWp | h/day | Perf. % | kWh/day (illus.) | Note |
|---|---|---|---|---|
| 3.0 | 4.5 | 80 | 10.8 | Small rooftop, moderate sun, realistic PR |
| 6.6 | 5.0 | 78 | 25.7 | Common AU residential size, decent site |
| 10 | 3.5 | 85 | 29.8 | Larger array, cloudier climate, efficient gear |
| 4.0 (10 × 400 W) | 4.0 | 100 | 16.0 | Upper bound before loss factor |
Real-World Examples
Quote sanity check
Installer quotes 7.2 kWp with an estimated 4.2 peak sun hours and 80% performance → 7.2 × 4.2 × 0.8 ≈ 24.2 kWh/day. Compare to their production report and your eventual utility data.
Seasonal swing
Summer might be 5.5 h and winter 2.5 h for the same roof — this tool uses one number at a time, so run it twice if you want summer vs winter ballparks.
Micro-inverters vs string
Different topologies change shading tolerance and clipping; both are usually absorbed into the single performance % unless you model hour-by-hour.
EV miles from solar
If you estimate 18 kWh/day and your EV averages 3.5 mi/kWh, that is roughly 63 miles of charge per average day before losses in the car charger.
FAQ
They are not “hours of daylight.” One peak sun hour means the same solar energy as one hour at the reference 1 kW/m² intensity. Maps and installers often quote a daily average for your location.
If you have a PV designer’s performance ratio, use that. Otherwise 75–85% is a common residential planning range; 100% ignores real losses and overstates output.
Module ratings are DC (kWp). Inverter AC output capacity (kWac) can limit clipped midday power on large arrays; that effect can be folded into your performance % for simple estimates.
If the kWp field has a valid number, it is used and the per-panel inputs are ignored until you clear kWp, same pattern as our other dual-path calculators.
Apps show instantaneous power, self-consumption, battery charge, and weather for today — this tool predicts average daily energy from averages you supply. They should be in the same ballpark over long periods.
Convert power and time with the Watts to kWh Calculator, average power from monthly energy with kWh to Watts, and costs with the Electricity Cost Calculator using your estimated daily kWh.