Solar Panel Sizing Calculator
Estimate required PV array kW from daily energy use, peak sun hours, and system derate for industrial and commercial planning.
Quick answer
Array kW ≈ Daily kWh ÷ (Peak sun hours × System efficiency). Example: 40 kWh/day, 5.0 PSH, 0.80 derate → 10.0 kW array. Next: estimate annual yield in the PV energy production calculator. Temporary hub: Solar calculator.
Quick Solar Panel Sizing Calculator
Defaults: 40 kWh/day · 5.0 peak sun hours · 0.80 system efficiency.
40 kWh/day ÷ (5.0 × 0.80) = 10.0 kW DC array.
Advanced Solar Panel Sizing Calculator
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Solar Panel Sizing Results
Engineering disclaimer
Planning estimate only. Confirm irradiance, shading, and utility interconnection with site data and OEM software before procurement.
Results
10.0 kW array — default example.
Array kW by peak sun hours
Same daily kWh and derate; highlights how PSH changes array size.
| Peak sun hours | Array kW | Approx. modules |
|---|
People also ask
- How do I size a solar array? Array kW ≈ daily kWh ÷ (PSH × derate).
- How many watts of solar panels do I need? Array watts = array kW × 1000; module count ≈ array watts ÷ module watts.
- What are peak sun hours? Equivalent full-sun hours at 1,000 W/m²—not daylight length.
- Is this for camping kits? No—industrial/commercial planning; not portable power stations.
Planning guidance
- Derate honestly: Soiling and high temperature often pull efficiency below 0.80 on industrial roofs.
- Load first: Screen plant demand with the factory load calculator before locking array kW.
- Yield next: Convert array kW to annual kWh in the PV energy production calculator.
- BOS: Size charge controllers in the MPPT sizing calculator.
- Path: Full workflow on the Solar calculator hub.
Typical scenarios
- Warehouse roof: 60–120 kWh/day process + lighting offset—PSH 4.5–5.5 typical mid-latitudes.
- Office campus: 15–40 kWh/day daytime-heavy load—pair with production estimate for bill offset.
- Low-sun site: PSH 3.0–3.8 drives larger arrays—confirm before inverter/MPPT quotes.
Formula (quick reference)
Array kW = Daily kWh ÷ (Peak sun hours × System efficiency)
Module count ≈ (Array kW × 1000) ÷ Module watts. See worked examples. Method walkthrough: how to size a commercial solar array. For derate η, read solar system losses & derating.
Frequently Asked Questions
How do I calculate solar panel array size?
Divide daily kWh by peak sun hours times system efficiency (derate). Example: 40 ÷ (5 × 0.8) = 10 kW.
How many watts of solar panels do I need?
First get array kW from daily kWh ÷ (PSH × derate), then array watts = array kW × 1000. Enter optional module nameplate watts to estimate count (e.g. 10 kW ÷ 450 W ≈ 23 modules). This page absorbs the “panel wattage calculator” intent—no separate wattage-only tool.
What peak sun hours should I use?
Use location peak sun hours from irradiance maps or site data—not clock hours of daylight.
How is this different from the energy estimator?
This sizes PV array kW from solar resource and derate. The energy estimator focuses on facility kWh cost, not PV array sizing.
Can I use this for portable power stations?
No. It targets industrial/commercial array planning, not camping or consumer kits.
What is the next step after array kW?
Estimate annual yield in the PV energy production calculator, then size MPPT controllers.
How it works
Daily AC energy demand is divided by peak sun hours and a combined system efficiency (inverter, wiring, soiling, temperature). The result is DC array nameplate kW for planning—not a bid-ready design.
Optional module wattage converts array kW into an approximate module count for BOM screening.
How many watts of solar panels do I need?
Array watts (W) = Array kW × 1000. Example: 40 kWh/day at 5.0 PSH and η=0.80 → 10.0 kW → 10,000 W of nameplate. At 450 W modules → about 23 panels. Use this calculator when search intent is “solar panel wattage” or “how many watts do I need”—same formula as array sizing.
Formula and sources
Array kW = Daily kWh ÷ (PSH × η_system)
Use site PSH and conservative η (often 0.75–0.85). Confirm with OEM design software before procurement.
Worked examples
- 40 kWh/day at 5.0 PSH, η=0.80
40 ÷ (5 × 0.80) = 10.0 kW. At 450 W modules ≈ 23 panels.
- 80 kWh/day warehouse, 4.5 PSH
80 ÷ (4.5 × 0.80) ≈ 22.2 kW array.