{
    "name": "Solar Inverter Sizing Calculator",
    "url": "https://calculators.geekmidst.com/calculators/solar-inverter-sizing-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/solar-inverter-sizing-calculator.md",
    "category": "Energy & environment",
    "description": "Size a solar inverter from array kWp and a DC/AC ratio, and check the maximum panels per string from cold-weather Voc and the inverter voltage limit.",
    "summary": "An inverter is sized from the array’s DC rating divided by a chosen DC/AC ratio. Strings must also stay below the inverter’s maximum DC voltage on the coldest morning, when panel voltage is highest.",
    "also_called": [
        "String sizing calculator",
        "DC/AC ratio 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": "dc_kw",
            "label": "Array size (DC)",
            "type": "number",
            "default": "6.6",
            "unit": "kWp"
        },
        {
            "name": "ratio",
            "label": "DC/AC ratio",
            "type": "number",
            "default": "1.2"
        },
        {
            "name": "voc",
            "label": "Panel open-circuit voltage (Voc)",
            "type": "number",
            "default": "49.5",
            "unit": "V"
        },
        {
            "name": "temp_coeff",
            "label": "Voc temperature coefficient",
            "type": "number",
            "default": "-0.27",
            "unit": "%/°C"
        },
        {
            "name": "t_min",
            "label": "Lowest expected cell temperature",
            "type": "number",
            "default": "-10",
            "unit": "°C"
        },
        {
            "name": "vmax",
            "label": "Inverter maximum DC input voltage",
            "type": "number",
            "default": "600",
            "unit": "V"
        }
    ],
    "outputs": [
        {
            "key": "ac_kw",
            "label": "Inverter AC rating",
            "format": "number"
        },
        {
            "key": "voc_cold",
            "label": "Panel Voc at the lowest temperature",
            "format": "number"
        },
        {
            "key": "max_modules",
            "label": "Maximum panels per string",
            "format": "integer"
        },
        {
            "key": "string_voc",
            "label": "Cold Voc of that string",
            "format": "number"
        }
    ],
    "formula": {
        "text": "AC kW = DC kWp ÷ DC/AC ratio;  Voc(cold) = Voc × (1 + β × (Tmin − 25));  Max panels per string = ⌊Vmax ÷ Voc(cold)⌋",
        "variables": {
            "β": "Voc temperature coefficient as a fraction per °C (negative)",
            "Tmin": "lowest cell temperature, °C",
            "Vmax": "inverter maximum DC input voltage"
        }
    },
    "worked_example": {
        "inputs": {
            "dc_kw": "6.6",
            "ratio": "1.2",
            "voc": "49.5",
            "temp_coeff": "-0.27",
            "t_min": "-10",
            "vmax": "600"
        },
        "steps": [
            "AC rating = 6.6 ÷ 1.2 = 5.5 kW.",
            "Voc at −10 °C = 49.5 × (1 + (−0.0027) × (−35)) = 49.5 × 1.0945 = 54.18 V.",
            "Panels per string = 600 ÷ 54.18 = 11.07, so at most 11."
        ],
        "result": "A 6.6 kWp array at a 1.2 ratio suits a 5.5 kW inverter, with no more than 11 of these panels per string on a 600 V input."
    },
    "interpretation": "A ratio above 1 slightly clips output on the sunniest hours but makes better use of the inverter the rest of the time. The string limit is a hard safety limit: exceeding the inverter’s maximum voltage can damage it.",
    "assumptions": [
        "The temperature coefficient is linear over the range.",
        "All strings use identical panels."
    ],
    "limitations": [
        "Does not check the MPPT voltage window, maximum input current or minimum string length; check them against the datasheets.",
        "Local electrical codes may require extra margins; a qualified installer must design the final system."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "Why does panel voltage rise in the cold?",
            "answer": "Silicon cell voltage falls as temperature rises and rises as it falls. On a clear, freezing morning the open-circuit voltage is at its highest."
        },
        {
            "question": "Is it safe to oversize the array?",
            "answer": "Within the inverter maker’s stated DC limits, yes; the inverter simply caps its AC output. Never exceed the maximum DC voltage or current."
        }
    ],
    "sources": [],
    "related": [
        {
            "name": "Solar PV System Sizing Calculator",
            "url": "https://calculators.geekmidst.com/calculators/solar-pv-system-sizing-calculator"
        },
        {
            "name": "Solar Payback Calculator",
            "url": "https://calculators.geekmidst.com/calculators/solar-payback-calculator"
        },
        {
            "name": "Three-Phase Power Calculator",
            "url": "https://calculators.geekmidst.com/calculators/three-phase-power-calculator"
        }
    ],
    "disclaimer": "Quantities are estimates. Confirm requirements with your engineer or supplier before ordering materials.",
    "publisher": "GM¹X CalcVerse"
}