How many solar panels do I need?
Set your usage and site factors, then click Calculate size.
Adds to required kW before panel count (rough planning).
Click Calculate size for kW, panels, roof area, and production.
City sunlight presets (illustrative)
Adjusts peak sun hours only—click Calculate size after choosing.
Daily & monthly production (sized system)
Click Calculate size for estimated kWh/day and kWh/month from the sized array.
Seasonal variation (winter vs summer)
Click Calculate size for rough winter/summer daily kWh using your factors.
Cost estimate
Click Calculate size for total cost from kW × cost per kW.
Size comparison (sample monthly kWh)
| Monthly kWh | Approx. kW | Panels (@ W) |
|---|---|---|
| Click Calculate size to fill the table. | ||
Roof layout preview (schematic)
One square ≈ one module; rows wrap for readability—not to scale.
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How to size a solar system?
Start from your monthly kWh (from bills or our Electricity Bill Calculator). Convert to an average daily need, then divide by expected kWh per kW per day from sun hours and realistic performance and loss factors. That yields an approximate DC kW of PV; divide by module watts for panel count, and multiply by area per panel for roof footprint.
How many panels do I need?
Panels required = ceil(system kW × 1000 ÷ module wattage). Arrays are often slightly oversized or split across orientations—your installer finalizes strings and inverter loading.
What affects solar output?
Irradiance (location, season), tilt/azimuth, shading, module temperature, inverter efficiency, and soiling all change real output versus nameplate kW.
Embed
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FAQ
- How many solar panels do I need?
- Divide the required array kilowatts by each panel’s kilowatts and round up. Add spare capacity if you expect higher future use or clipping rules.
- What size solar system for home?
- Match annual or monthly consumption you want to offset, your budget, and roof space. Net metering caps and load patterns also matter.
- How much roof space is required?
- Multiply panel count by roughly 1.7–2.2 m² per module including gaps; add walkways and setbacks per local fire codes.
- How to calculate solar capacity?
- Use average daily kWh divided by kWh per kW per day from sun hours and derating, or use this calculator with your bill data.