{
  "slug": "how-many-solar-panels-do-i-need",
  "title": "How Many Solar Panels Do I Need?",
  "heading": "How Many Solar Panels Do I Need?",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/how-many-solar-panels-do-i-need",
  "summary": "A household using 900 kWh a month in a region with 5 peak sun hours needs about 16 standard 400W panels.",
  "description": "Solar panel sizing starts from your monthly energy usage, converts it to a daily average, and divides by how much energy one panel produces per day given your region's peak sun hours and the panel's wattage, then adds a system inefficiency buffer for inverter and wiring losses.",
  "formula": "Daily kWh Needed = Monthly kWh ÷ 30. Panel Output (kWh/day) = Panel Watts × Peak Sun Hours ÷ 1000 × System Efficiency. Panels Needed = Daily kWh Needed ÷ Panel Output.",
  "dateModified": "2026-09-06",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=how-many-solar-panels-do-i-need",
  "inputs": [
    {
      "id": "monthlyKwh",
      "label": "Monthly electricity usage",
      "kind": "number",
      "hint": null,
      "default": 900,
      "unit": "kWh",
      "min": 50,
      "max": null
    },
    {
      "id": "sunHours",
      "label": "Peak sun hours per day",
      "kind": "number",
      "hint": null,
      "default": 5,
      "unit": "hrs",
      "min": 2,
      "max": 8
    },
    {
      "id": "panelWatts",
      "label": "Panel wattage",
      "kind": "number",
      "hint": null,
      "default": 400,
      "unit": "W",
      "min": 100,
      "max": 600
    },
    {
      "id": "systemEfficiency",
      "label": "System efficiency",
      "kind": "number",
      "hint": null,
      "default": 80,
      "unit": "%",
      "min": 60,
      "max": 95
    }
  ],
  "outputs": [
    {
      "id": "panelsNeeded",
      "label": "Solar panels needed",
      "format": "number",
      "hint": null,
      "primary": true
    },
    {
      "id": "systemSizeKw",
      "label": "Total system size (kW)",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "dailyKwh",
      "label": "Daily energy needed (kWh)",
      "format": "decimal",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Monthly electricity usage: 900 kWh",
      "Peak sun hours per day: 5 hrs",
      "Panel wattage: 400 W",
      "System efficiency: 80 %"
    ],
    "outputs": [
      "Solar panels needed: 19",
      "Total system size (kW): 7.6",
      "Daily energy needed (kWh): 30"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter monthly electricity usage (kWh).",
      "Enter peak sun hours per day (hrs).",
      "Enter panel wattage (W).",
      "Enter system efficiency (%).",
      "Read your solar panels needed 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": 540,
        "sunHours": 3,
        "panelWatts": 240,
        "systemEfficiency": 60
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "monthlyKwh": 900,
        "sunHours": 5,
        "panelWatts": 400,
        "systemEfficiency": 80
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "monthlyKwh": 1440,
        "sunHours": 8,
        "panelWatts": 600,
        "systemEfficiency": 95
      }
    }
  ],
  "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 many solar panels do I need?",
      "a": "For 900 kWh/month usage with 5 peak sun hours a day, 400W panels, and 80% system efficiency, you need about 19 panels, forming a roughly 7.5 kW system."
    },
    {
      "q": "What are 'peak sun hours'?",
      "a": "It's the equivalent number of hours per day sunlight is intense enough to produce a panel's rated output — sunny states like Arizona average 6-7 hours, while cloudier northern regions average 3-4."
    },
    {
      "q": "Why include a system efficiency factor?",
      "a": "Real-world solar systems lose 15-25% of rated output to inverter conversion, wiring resistance, panel soiling, and temperature effects, so ignoring this understates the panels you actually need."
    },
    {
      "q": "Does roof space limit how many panels I can install?",
      "a": "Yes — a standard 400W panel is about 18 sq ft, so a 19-panel system needs roughly 340 sq ft of usable, unshaded roof space, which can be a constraint on smaller roofs."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/how-much-will-my-electric-bill-be",
    "https://www.revenuelab.fyi/toolbox/how-much-to-run-an-air-conditioner"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — How Many Solar Panels Do I Need? (https://www.revenuelab.fyi/toolbox/how-many-solar-panels-do-i-need)"
}