{
    "name": "Solar Rooftop Area Calculator",
    "url": "https://calculators.geekmidst.com/calculators/solar-rooftop-area-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/solar-rooftop-area-calculator.md",
    "category": "Construction",
    "description": "Work out how many solar panels a target system size needs, the roof area they take up, and the largest system that fits on the roof you have.",
    "summary": "Divide the system size by the panel rating to get the panel count, multiply by panel area, then allow for gaps, edge setbacks and obstructions with a usable-area fraction.",
    "also_called": [
        "Solar panel roof space calculator"
    ],
    "applies_to": "Worldwide",
    "last_updated": "2026-10-29",
    "computation": "Results are computed in the visitor’s browser on the HTML page. This API describes the calculator; it does not compute results.",
    "inputs": [
        {
            "name": "target_kw",
            "label": "Target system size",
            "type": "number",
            "default": "5",
            "unit": "kWp"
        },
        {
            "name": "panel_watt",
            "label": "Panel rating",
            "type": "number",
            "default": "450",
            "unit": "W"
        },
        {
            "name": "panel_length",
            "label": "Panel length",
            "type": "number",
            "default": "1.9",
            "unit": "m"
        },
        {
            "name": "panel_width",
            "label": "Panel width",
            "type": "number",
            "default": "1.1",
            "unit": "m"
        },
        {
            "name": "usable_fraction",
            "label": "Usable share of roof",
            "type": "number",
            "default": "0.75"
        },
        {
            "name": "roof_area",
            "label": "Available roof area",
            "type": "number",
            "default": "50",
            "unit": "m²",
            "optional": true
        }
    ],
    "outputs": [
        {
            "key": "roof_needed",
            "label": "Roof area needed",
            "format": "number"
        },
        {
            "key": "panels",
            "label": "Panels needed",
            "format": "integer"
        },
        {
            "key": "actual_kw",
            "label": "Installed size",
            "format": "number"
        },
        {
            "key": "panel_area",
            "label": "Panel area",
            "format": "number"
        },
        {
            "key": "fits",
            "label": "On your roof",
            "format": "text"
        },
        {
            "key": "max_panels",
            "label": "Most panels that fit",
            "format": "integer"
        },
        {
            "key": "max_kw",
            "label": "Largest system that fits",
            "format": "number"
        }
    ],
    "formula": {
        "text": "Panels = ⌈Target W ÷ Panel W⌉;  Roof needed = Panels × Length × Width ÷ Usable share;  Max panels = ⌊Roof × Usable share ÷ Panel area⌋",
        "variables": {
            "Usable share": "fraction of the roof that can hold panels"
        }
    },
    "worked_example": {
        "inputs": {
            "target_kw": "5",
            "panel_watt": "450",
            "panel_length": "1.9",
            "panel_width": "1.1",
            "usable_fraction": "0.75",
            "roof_area": "50"
        },
        "steps": [
            "Panels = ⌈5,000 ÷ 450⌉ = 12 (5.4 kWp).",
            "Panel area = 12 × 1.9 × 1.1 = 25.08 m²; ÷ 0.75 = 33.44 m² of roof.",
            "A 50 m² roof holds ⌊50 × 0.75 ÷ 2.09⌋ = 17 panels = 7.65 kWp."
        ],
        "result": "A 5 kW target needs 12 panels of 450 W and about 33 m² of roof; a 50 m² roof could take up to 7.65 kWp."
    },
    "interpretation": "Use this for an early feasibility check. Orientation, tilt, shading and roof structure decide whether the space is worth using.",
    "assumptions": [
        "All panels are the same size and rating.",
        "The usable share covers row gaps and setbacks."
    ],
    "limitations": [
        "Does not estimate energy yield.",
        "Roof loading, wind uplift and local setback rules need checking by an installer."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "Why round the panel count up?",
            "answer": "You cannot install part of a panel, so meeting the target means the next whole panel, which slightly exceeds it."
        },
        {
            "question": "Does a sloped roof change the area?",
            "answer": "Enter the sloped roof area you can mount on; panels lie flat on the roof plane."
        }
    ],
    "sources": [],
    "related": [
        {
            "name": "Rainwater Harvesting Tank Calculator",
            "url": "https://calculators.geekmidst.com/calculators/rainwater-harvesting-tank-calculator"
        },
        {
            "name": "ROI Calculator",
            "url": "https://calculators.geekmidst.com/calculators/roi-calculator"
        },
        {
            "name": "Break-even Calculator",
            "url": "https://calculators.geekmidst.com/calculators/break-even-calculator"
        }
    ],
    "disclaimer": "Quantities are estimates. Confirm requirements with your engineer or supplier before ordering materials.",
    "publisher": "GM¹X CalcVerse"
}