{
  "id": "v20-uk-solar-payback",
  "version": "20.16.0",
  "name": "Solar Payback Calculator — United Kingdom",
  "shortName": "Solar Payback",
  "description": "Compare a simple first-year payback with a discounted cash-flow model that explicitly includes replacement and declining generation. GBP planning view; stated limitations apply.",
  "category": "Home & Construction",
  "categorySlug": "home-construction",
  "keywords": [
    "solar-payback",
    "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-payback.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-payback/",
    "definition": "/uk/solar-payback/definition.json",
    "schema": "/uk/solar-payback/schema.json",
    "llms": "/uk/solar-payback/llms.txt",
    "legacyDefinition": "/uk/solar-payback/definition.json"
  },
  "queryExample": "https://askcalculators.com/uk/solar-payback/?projectCost=18000&confirmedIncentive=0&annualBenefit=1800&maintenance=100&years=25&discountRate=4&degradation=0.5&energyEscalation=2&replacementYear=0&replacementCost=0",
  "queryParameters": {
    "projectCost": {
      "label": "Installed project price",
      "type": "money",
      "required": true,
      "default": 18000
    },
    "confirmedIncentive": {
      "label": "Confirmed eligible incentive",
      "type": "money",
      "required": true,
      "default": 0
    },
    "annualBenefit": {
      "label": "First-year gross bill and export benefit",
      "type": "money",
      "required": true,
      "default": 1800
    },
    "maintenance": {
      "label": "Annual maintenance",
      "type": "money",
      "required": true,
      "default": 100
    },
    "years": {
      "label": "Planning horizon, years",
      "type": "number",
      "required": true,
      "default": 25
    },
    "discountRate": {
      "label": "Annual discount rate",
      "type": "percent",
      "required": true,
      "default": 4
    },
    "degradation": {
      "label": "Annual output degradation",
      "type": "percent",
      "required": true,
      "default": 0.5
    },
    "energyEscalation": {
      "label": "Annual energy-price escalation",
      "type": "percent",
      "required": true,
      "default": 2
    },
    "replacementYear": {
      "label": "Replacement year (0 means none)",
      "type": "number",
      "required": true,
      "default": 0
    },
    "replacementCost": {
      "label": "Replacement cost",
      "type": "money",
      "required": true,
      "default": 0
    }
  },
  "inputs": [
    {
      "id": "projectCost",
      "label": "Installed project price",
      "type": "money",
      "defaultValue": 18000,
      "required": true,
      "min": 0,
      "max": 1000000000000,
      "step": 0.01,
      "prefix": "GBP",
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "confirmedIncentive",
      "label": "Confirmed eligible incentive",
      "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": "annualBenefit",
      "label": "First-year gross bill and export benefit",
      "type": "money",
      "defaultValue": 1800,
      "required": true,
      "min": 0,
      "max": 1000000000000,
      "step": 0.01,
      "prefix": "GBP",
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "maintenance",
      "label": "Annual maintenance",
      "type": "money",
      "defaultValue": 100,
      "required": true,
      "min": 0,
      "max": 1000000000000,
      "step": 0.01,
      "prefix": "GBP",
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "years",
      "label": "Planning horizon, years",
      "type": "number",
      "defaultValue": 25,
      "required": true,
      "min": 1,
      "max": 50,
      "step": 1,
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "discountRate",
      "label": "Annual discount rate",
      "type": "percent",
      "defaultValue": 4,
      "required": true,
      "min": 0,
      "max": 50,
      "step": 0.1,
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "degradation",
      "label": "Annual output degradation",
      "type": "percent",
      "defaultValue": 0.5,
      "required": true,
      "min": 0,
      "max": 20,
      "step": 0.1,
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "energyEscalation",
      "label": "Annual energy-price escalation",
      "type": "percent",
      "defaultValue": 2,
      "required": true,
      "min": 0,
      "max": 25,
      "step": 0.1,
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "replacementYear",
      "label": "Replacement year (0 means none)",
      "type": "number",
      "defaultValue": 0,
      "required": true,
      "min": 0,
      "max": 50,
      "step": 1,
      "help": "Illustrative starting value; replace with your own evidence."
    },
    {
      "id": "replacementCost",
      "label": "Replacement cost",
      "type": "money",
      "defaultValue": 0,
      "required": true,
      "min": 0,
      "max": 1000000000000,
      "step": 0.01,
      "prefix": "GBP",
      "help": "Illustrative starting value; replace with your own evidence."
    }
  ],
  "outputs": [
    {
      "id": "capital",
      "label": "Net capital cost",
      "format": "currency",
      "digits": 2,
      "currency": "GBP"
    },
    {
      "id": "annualSaving",
      "label": "First-year net saving",
      "format": "currency",
      "digits": 2,
      "currency": "GBP"
    },
    {
      "id": "payback",
      "label": "Simple payback, years",
      "format": "number",
      "digits": 2,
      "primary": true
    },
    {
      "id": "npv",
      "label": "Discounted net value",
      "format": "currency",
      "digits": 2,
      "currency": "GBP"
    },
    {
      "id": "breakeven",
      "label": "Cash-flow break-even year",
      "format": "number",
      "digits": 2
    },
    {
      "id": "cumulative",
      "label": "Undiscounted lifetime net benefit",
      "format": "currency",
      "digits": 2,
      "currency": "GBP"
    }
  ],
  "formula": {
    "expression": "simple payback = (project price − confirmed incentive) ÷ (first-year benefit − annual maintenance).",
    "note": "Inputs are converted to canonical units before evaluating this stated formula."
  },
  "examples": [
    {
      "label": "Illustrative defaults; required verification checks remain unconfirmed",
      "inputs": {
        "unitSystem": "metric",
        "projectCost": 18000,
        "confirmedIncentive": 0,
        "annualBenefit": 1800,
        "maintenance": 100,
        "years": 25,
        "discountRate": 4,
        "degradation": 0.5,
        "energyEscalation": 2,
        "replacementYear": 0,
        "replacementCost": 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-payback",
  "namespace": "uk",
  "countries": [
    "us",
    "ca",
    "uk",
    "ie"
  ]
}