Solar Sizing Calculator

Estimate solar panel array and battery storage size

Size your solar system from real consumption

Energy Use
Average monthly usage in kilowatt-hours from your utility bill or monitoring app. Annual use equals monthly use times 12.
Peak sun hours are the daily average of strong sunlight. They vary by latitude and climate; the calculator uses them as the kWh per kilowatt of array produced per day.
Array
Leave at 0 to skip the roof area check. Needed area assumes a panel footprint of about 5.5 sq ft per kilowatt.
Array Size
0kW
Panels Needed
0panels
Total Panel Power
0W
Roof Area Needed
0sq ft
Battery Storage
Battery Capacity
0kWh
Daily Use
0kWh

How This Solar Sizing Calculator Works

The calculator starts from your monthly electricity use in kilowatt-hours. It converts that into an annual consumption figure, divides by the peak sun hours of your chosen location times 365, and produces the required array size in kilowatts. Dividing by your panel wattage gives the number of panels, and multiplying by the panel footprint gives the roof area.

The battery block converts your average daily consumption into the storage capacity that covers your chosen autonomy at your depth of discharge and round-trip efficiency. Presets cover a typical residential rooftop, an off-grid cabin and an EV-charging offset so you can sanity-check the numbers before entering your own figures.

Why This Beats Asking an AI Chatbot

AI chatbots cannot run the sizing arithmetic reliably, cannot combine roof area with real consumption, cannot apply depth of discharge and efficiency correctly, and will often invent panel counts. A deterministic browser calculator runs the same formulas every time, so the answer is reproducible and auditable, and you can copy a plain-text sizing report to take to a solar installer.

Frequently Asked Questions

How do I calculate how many solar panels I need?

Divide your annual kilowatt-hour use by the peak sun hours of your location times 365. The result is the array size in kilowatts; divide by panel wattage to get the panel count and round up. The solar sizing calculator does all of this from monthly use in one step.

How is battery storage sized for solar?

Battery capacity equals average daily consumption times the autonomy days you want, divided by the depth of discharge and the round-trip efficiency. The calculator outputs the required capacity in kilowatt-hours directly.

What are peak sun hours and why do they matter?

Peak sun hours measure daily strong sunlight for photovoltaic output, averaged over the year. They vary sharply by region, so the same panel produces about twice the annual energy in the Southwest as in the Pacific Northwest.

Can an AI chatbot size my solar panel system?

No. Chatbots cannot run the sizing math, integrate roof area with consumption, or apply battery losses. They will often produce confidently wrong array sizes; this calculator computes each step deterministically.

How much roof area do I need for solar panels?

Each kilowatt of array needs roughly 5.5 square feet of roof area at a typical 400 watt panel. The calculator multiplies the required kilowatts by the panel footprint and rounds to whole panels.

Is my energy usage data private with this calculator?

Yes. All math runs in the browser. Monthly use, roof area and battery settings never leave the page.

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