{
  "id": "v20-uk-solar-sizing",
  "version": "20.16.0",
  "name": "Solar Panel Sizing Calculator — United Kingdom",
  "shortName": "Solar Panel Sizing",
  "description": "Translate a site-specific annual energy target into a rounded panel count and a transparent material-cost scenario. GBP planning view; stated limitations apply.",
  "category": "Home & Construction",
  "categorySlug": "home-construction",
  "keywords": [
    "solar-sizing",
    "uk",
    "energy-conservation",
    "pvwatts",
    "energy-saver"
  ],
  "status": "live",
  "workStatus": "pending",
  "reviewStatus": "pending",
  "migrationStatus": "new",
  "engine": "native",
  "creator": null,
  "reviewer": null,
  "quality": {
    "availability": "live",
    "technicalReviewRecord": "/reviews/v20-uk-solar-sizing.json",
    "qualifiedReview": "pending",
    "qualifiedReviewer": null,
    "qualifiedReviewDate": null,
    "formulaVersion": "20.16.0",
    "referenceCoverage": "references-listed",
    "releaseTestScope": "Catalog and regression checks are not a professional formula audit; consult release evidence.",
    "historicalMetadataDate": "",
    "historicalMetadataNotice": "The imported date is not evidence of a completed human review."
  },
  "notice": "Illustrative defaults are not local quotes or verified legal rules. Dated reference components and user-entered assumptions are explicitly distinguished. Professional review is pending.",
  "urls": {
    "page": "/uk/solar-sizing/",
    "definition": "/uk/solar-sizing/definition.json",
    "schema": "/uk/solar-sizing/schema.json",
    "llms": "/uk/solar-sizing/llms.txt",
    "legacyDefinition": "/uk/solar-sizing/definition.json"
  },
  "queryExample": "https://askcalculators.com/uk/solar-sizing/?unitSystem=metric&annualUse=10000&offset=80&specificYield=1200&panelWatts=420&panelArea=2&layoutAllowance=20&unitRate=0&laborCost=0&deliveryCost=0&otherCost=0&costMultiplier=1&spreadPercent=15&taxRate=0",
  "queryParameters": {
    "unitSystem": {
      "label": "Measurement system",
      "type": "select",
      "required": false,
      "default": "metric"
    },
    "annualUse": {
      "label": "Annual electricity use, kWh",
      "type": "number",
      "required": true,
      "default": 10000
    },
    "offset": {
      "label": "Target annual generation / use",
      "type": "percent",
      "required": true,
      "default": 80
    },
    "specificYield": {
      "label": "Site-specific annual yield, kWh per kW",
      "type": "number",
      "required": true,
      "default": 1200
    },
    "panelWatts": {
      "label": "Panel nameplate output, W",
      "type": "number",
      "required": true,
      "default": 420
    },
    "panelArea": {
      "label": "Area of one panel",
      "type": "number",
      "required": true,
      "default": 2
    },
    "layoutAllowance": {
      "label": "Roof-layout allowance beyond panel area",
      "type": "percent",
      "required": true,
      "default": 20
    },
    "unitRate": {
      "label": "Material price per panel",
      "type": "money",
      "required": true,
      "default": 0
    },
    "laborCost": {
      "label": "Total labor allowance",
      "type": "money",
      "required": true,
      "default": 0
    },
    "deliveryCost": {
      "label": "Delivery allowance",
      "type": "money",
      "required": true,
      "default": 0
    },
    "otherCost": {
      "label": "Other fixed costs",
      "type": "money",
      "required": true,
      "default": 0
    },
    "costMultiplier": {
      "label": "Material/labor multiplier",
      "type": "number",
      "required": true,
      "default": 1
    },
    "spreadPercent": {
      "label": "Low/high sensitivity around the entered total",
      "type": "percent",
      "required": true,
      "default": 15
    },
    "taxRate": {
      "label": "Explicit tax allowance",
      "type": "percent",
      "required": true,
      "default": 0
    }
  },
  "inputs": [
    {
      "id": "unitSystem",
      "label": "Measurement system",
      "type": "select",
      "defaultValue": "metric",
      "options": [
        {
          "value": "imperial",
          "label": "Imperial (US gallons / short tons where relevant)"
        },
        {
          "value": "metric",
          "label": "Metric"
        }
      ]
    },
    {
      "id": "annualUse",
      "label": "Annual electricity use, kWh",
      "type": "number",
      "defaultValue": 10000,
      "required": true,
      "min": 1,
      "max": 100000000,
      "step": 0.01,
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "offset",
      "label": "Target annual generation / use",
      "type": "percent",
      "defaultValue": 80,
      "required": true,
      "min": 0,
      "max": 300,
      "step": 0.1,
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "specificYield",
      "label": "Site-specific annual yield, kWh per kW",
      "type": "number",
      "defaultValue": 1200,
      "required": true,
      "min": 100,
      "max": 3000,
      "step": 0.01,
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "panelWatts",
      "label": "Panel nameplate output, W",
      "type": "number",
      "defaultValue": 420,
      "required": true,
      "min": 50,
      "max": 1000,
      "step": 0.01,
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "panelArea",
      "label": "Area of one panel",
      "type": "number",
      "defaultValue": 2,
      "required": true,
      "min": 0.1,
      "max": 10,
      "suffix": "m²",
      "unitConversion": {
        "factor": 0.09290304,
        "offset": 0,
        "inverse": false,
        "metric": "m²",
        "imperial": "ft²",
        "canonicalMin": 0.1,
        "canonicalMax": 10
      },
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "layoutAllowance",
      "label": "Roof-layout allowance beyond panel area",
      "type": "percent",
      "defaultValue": 20,
      "required": true,
      "min": 0,
      "max": 100,
      "step": 0.1,
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "unitRate",
      "label": "Material price per panel",
      "type": "money",
      "defaultValue": 0,
      "required": true,
      "min": 0,
      "max": 1000000000000,
      "step": 0.01,
      "help": "Zero means unpriced, not free. Enter a current, scoped supplier quote. Illustrative starting value; replace with your own evidence.",
      "prefix": "GBP"
    },
    {
      "id": "laborCost",
      "label": "Total labor allowance",
      "type": "money",
      "defaultValue": 0,
      "required": true,
      "min": 0,
      "max": 1000000000000,
      "step": 0.01,
      "prefix": "GBP",
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "deliveryCost",
      "label": "Delivery allowance",
      "type": "money",
      "defaultValue": 0,
      "required": true,
      "min": 0,
      "max": 1000000000000,
      "step": 0.01,
      "prefix": "GBP",
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "otherCost",
      "label": "Other fixed costs",
      "type": "money",
      "defaultValue": 0,
      "required": true,
      "min": 0,
      "max": 1000000000000,
      "step": 0.01,
      "prefix": "GBP",
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "costMultiplier",
      "label": "Material/labor multiplier",
      "type": "number",
      "defaultValue": 1,
      "required": true,
      "min": 0.1,
      "max": 10,
      "step": 0.01,
      "help": "Use a verified regional index only when supplied. 1 is an unadjusted scenario, not a researched index. Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "spreadPercent",
      "label": "Low/high sensitivity around the entered total",
      "type": "percent",
      "defaultValue": 15,
      "required": true,
      "min": 0,
      "max": 100,
      "step": 0.1,
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "taxRate",
      "label": "Explicit tax allowance",
      "type": "percent",
      "defaultValue": 0,
      "required": true,
      "min": 0,
      "max": 100,
      "step": 0.1,
      "help": "Illustrative starting value; replace with your own evidence."
    }
  ],
  "outputs": [
    {
      "id": "panels",
      "label": "Whole panels to order",
      "format": "number",
      "digits": 2
    },
    {
      "id": "installedKw",
      "label": "Installed nameplate capacity, kW",
      "format": "number",
      "digits": 2
    },
    {
      "id": "generation",
      "label": "Modeled annual generation, kWh",
      "format": "number",
      "digits": 2
    },
    {
      "id": "roofArea",
      "label": "Roof area allowance",
      "format": "number",
      "digits": 2,
      "unit": "area"
    },
    {
      "id": "materialCost",
      "label": "Material cost",
      "format": "currency",
      "digits": 2,
      "currency": "GBP"
    },
    {
      "id": "laborCost",
      "label": "Labor allowance",
      "format": "currency",
      "digits": 2,
      "currency": "GBP"
    },
    {
      "id": "deliveryCost",
      "label": "Delivery allowance",
      "format": "currency",
      "digits": 2,
      "currency": "GBP"
    },
    {
      "id": "otherCost",
      "label": "Other specified costs",
      "format": "currency",
      "digits": 2,
      "currency": "GBP"
    },
    {
      "id": "tax",
      "label": "Entered tax allowance",
      "format": "currency",
      "digits": 2,
      "currency": "GBP"
    },
    {
      "id": "low",
      "label": "Low cost scenario",
      "format": "currency",
      "digits": 2,
      "currency": "GBP"
    },
    {
      "id": "mid",
      "label": "Middle cost scenario",
      "format": "currency",
      "digits": 2,
      "primary": true,
      "currency": "GBP"
    },
    {
      "id": "high",
      "label": "High cost scenario",
      "format": "currency",
      "digits": 2,
      "currency": "GBP"
    }
  ],
  "formula": {
    "expression": "panels = ceiling(annual use × offset ÷ yield × 1,000 ÷ panel watts).",
    "note": "Inputs are converted to canonical units before evaluating this stated formula."
  },
  "examples": [
    {
      "label": "Illustrative defaults; required verification checks remain unconfirmed",
      "inputs": {
        "unitSystem": "metric",
        "annualUse": 10000,
        "offset": 80,
        "specificYield": 1200,
        "panelWatts": 420,
        "panelArea": 2,
        "layoutAllowance": 20,
        "unitRate": 0,
        "laborCost": 0,
        "deliveryCost": 0,
        "otherCost": 0,
        "costMultiplier": 1,
        "spreadPercent": 15,
        "taxRate": 0
      }
    }
  ],
  "sources": [
    {
      "label": "DOE energy-use arithmetic",
      "url": "https://www.energy.gov/energysaver/save-electricity-and-fuel/appliances-and-electronics/estimating-appliance-and-home"
    },
    {
      "label": "PVWatts: site-specific solar estimation",
      "url": "https://pvwatts.nlr.gov/"
    },
    {
      "label": "DOE insulation overview",
      "url": "https://www.energy.gov/energysaver/weatherize/insulation"
    }
  ],
  "publicSlug": "solar-sizing",
  "namespace": "uk",
  "countries": [
    "us",
    "ca",
    "uk",
    "ie"
  ]
}