{
  "slug": "solar-panel",
  "title": "Solar Panel Calculator",
  "heading": "Solar Panel Calculator",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/solar-panel",
  "summary": "System size, panel count, and payback period.",
  "description": "System size follows your annual usage divided by local sun hours and system losses. Payback depends far more on your utility rate than on panel efficiency — high-rate states pay back in six years, cheap-power states in fifteen.",
  "formula": "kW needed = Annual kWh ÷ (Sun hours × 365 × Efficiency factor). Payback = Net cost ÷ Annual savings.",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=solar-panel",
  "inputs": [
    {
      "id": "monthlyKwh",
      "label": "Monthly electricity use",
      "kind": "number",
      "hint": null,
      "default": 950,
      "unit": "kWh",
      "min": 0,
      "max": null
    },
    {
      "id": "sunHours",
      "label": "Peak sun hours per day",
      "kind": "number",
      "hint": null,
      "default": 4.5,
      "unit": null,
      "min": 1,
      "max": 8
    },
    {
      "id": "panelWatts",
      "label": "Panel wattage",
      "kind": "number",
      "hint": null,
      "default": 410,
      "unit": "W",
      "min": 100,
      "max": null
    },
    {
      "id": "costPerWatt",
      "label": "Installed cost per watt",
      "kind": "number",
      "hint": null,
      "default": 3,
      "unit": "$",
      "min": 0.5,
      "max": null
    },
    {
      "id": "rate",
      "label": "Electricity rate",
      "kind": "number",
      "hint": null,
      "default": 0.17,
      "unit": "$/kWh",
      "min": 0.01,
      "max": null
    },
    {
      "id": "incentive",
      "label": "Tax credit and rebates",
      "kind": "number",
      "hint": null,
      "default": 30,
      "unit": "%",
      "min": 0,
      "max": 70
    }
  ],
  "outputs": [
    {
      "id": "kw",
      "label": "System size (kW)",
      "format": "decimal",
      "hint": null,
      "primary": true
    },
    {
      "id": "panels",
      "label": "Panels needed",
      "format": "number",
      "hint": null,
      "primary": false
    },
    {
      "id": "gross",
      "label": "Gross installed cost",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "net",
      "label": "Net cost after incentives",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "savings",
      "label": "Annual electricity savings",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "payback",
      "label": "Payback period (years)",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "twentyYear",
      "label": "20-year net benefit",
      "format": "currency",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Monthly electricity use: 950 kWh",
      "Peak sun hours per day: 4.5",
      "Panel wattage: 410 W",
      "Installed cost per watt: 3 $",
      "Electricity rate: 0.17 $/kWh",
      "Tax credit and rebates: 30 %"
    ],
    "outputs": [
      "System size (kW): 8.68",
      "Panels needed: 22",
      "Gross installed cost: $26,027.40",
      "Net cost after incentives: $18,219.18",
      "Annual electricity savings: $1,938.00",
      "Payback period (years): 9.4",
      "20-year net benefit: $20,540.82"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter monthly electricity use (kWh).",
      "Enter peak sun hours per day.",
      "Enter panel wattage (W).",
      "Enter installed cost per watt ($).",
      "Enter electricity rate ($/kWh).",
      "Enter tax credit and rebates (%).",
      "Read your system size (kw) on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "monthlyKwh": 575,
        "sunHours": 2.6999999999999997,
        "panelWatts": 250,
        "costPerWatt": 1.7999999999999998,
        "rate": 0.17,
        "incentive": 18
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "monthlyKwh": 950,
        "sunHours": 4.5,
        "panelWatts": 410,
        "costPerWatt": 3,
        "rate": 0.17,
        "incentive": 30
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "monthlyKwh": 1525,
        "sunHours": 7.2,
        "panelWatts": 660,
        "costPerWatt": 4.800000000000001,
        "rate": 0.17,
        "incentive": 48
      }
    }
  ],
  "limitations": [
    "Estimates assume standard, average conditions — local rules, pricing, and materials vary.",
    "Results are rounded for readability; add a buffer before ordering, booking, or committing.",
    "Double-check anything with a real cost attached against a local quote."
  ],
  "faq": [
    {
      "q": "How does the solar panel calculator work?",
      "a": "System size follows your annual usage divided by local sun hours and system losses. Payback depends far more on your utility rate than on panel efficiency — high-rate states pay back in six years, cheap-power states in fifteen. The underlying maths is: kW needed = Annual kWh ÷ (Sun hours × 365 × Efficiency factor). Payback = Net cost ÷ Annual savings."
    },
    {
      "q": "What do I need to enter?",
      "a": "6 values: monthly electricity use, peak sun hours per day, panel wattage, installed cost per watt, electricity rate, and tax credit and rebates. Each field starts with a sensible default, so you can change one number at a time and watch the result move."
    },
    {
      "q": "What does the system size (kw) result mean?",
      "a": "It is returned as a decimal number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds."
    },
    {
      "q": "Is this calculator free, and do I need an account?",
      "a": "Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser."
    },
    {
      "q": "How accurate is the result?",
      "a": "It applies the standard formula exactly, so the arithmetic is precise. Estimates assume standard, average conditions — local rules, pricing, and materials vary."
    },
    {
      "q": "Who is this tool for?",
      "a": "It's built for anyone doing everyday planning maths — a quick estimate that would otherwise need four browser tabs and a calculator app."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/electricity-cost",
    "https://www.revenuelab.fyi/toolbox/hvac-sizing",
    "https://www.revenuelab.fyi/toolbox/roi"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Solar Panel Calculator (https://www.revenuelab.fyi/toolbox/solar-panel)"
}