Property Valuation API

The Property Valuation API provides automated property valuations using two complementary methods: the House Price Index (HPI) method and the Comparable Sales method. Each valuation includes a confidence score and detailed breakdown of the calculation methodology.

Valuation methods:

• HPI Method — Applies regional house price index changes from the property's last sale date to the present, adjusting the original sale price for market movements
• Comparables Method — Calculates a weighted average price per m² from recent nearby sales, adjusted for property type, size similarity, and sale recency
• Cross-validation — When both methods produce results, they are cross-validated to boost confidence when values agree

Data included in the response:

• Property details — address, floor area, property type, last sale information
• Valuation results — recommended value, valuation range (low/mid/high), per-method breakdowns with confidence scores
• EPC data — energy ratings, tenure, construction details, heating information
• Comparable sales — up to 20 nearby comparable sales used in the calculation

This API is ideal for:

• Property platforms requiring automated valuations
• Mortgage brokers and lenders needing quick property value estimates
• Estate agents building valuation tools
• Property investors analysing potential purchases with extension or renovation scenarios
• PropTech applications needing valuation data in one API call

All requests to the Property Valuation API require authentication using an API key. You can obtain your API key from your PropertyInsights dashboard after subscribing to an API plan.

Include your API key in the request header as follows:

X-API-Key: your_api_key_here

Base URL

https://propertyinsights.co.uk/api/v1/

/property/valuation

Successful chargeable JSON responses include a top-level billing object. The endpoint examples on this page focus on the endpoint-specific data, so this repeated block may not be shown in every example.

"billing": {
  "mode": "prepaid",
  "creditsCharged": 1,
  "creditsRemaining": 1999,
  "creditsRefreshAt": "2026-08-14T09:30:00.000Z"
}

All authenticated API-key calls expose the billing headers, including validation errors and zero-credit status or management requests. Only successful chargeable JSON responses add the billing object to the response body.

The response is returned in JSON format with the following top-level structure:

{
  "success": true,
  "data": {
    "property": {
      "address": "10 Example Road",
      "postcode": "S11 8YH",
      "floorArea": 85,
      "propertyType": "House",
      "lastSale": {
        "price": 180000,
        "date": "2018-06-15",
        "pricePerM2": 2118
      }
    },
    "valuation": {
      "recommended": {
        "value": 245000,
        "method": "Comparables",
        "confidence": 78
      },
      "range": {
        "low": 230000,
        "mid": 245000,
        "high": 260000
      },
      "hpiMethod": {
        "value": 238000,
        "confidence": 62,
        "crossValidated": true,
        "agreementPct": "2.8",
        "details": {
          "lastSalePrice": 180000,
          "lastSaleDate": "2018-06-15",
          "indexAtSale": "112.50",
          "indexNow": "148.30",
          "indexChange": "31.82%",
          "monthsSinceSale": 91,
          "pricePerM2": 2800,
          "pricePerSqFt": 260,
          "priceChange": "32.2%",
          "priceChangeValue": 58000
        }
      },
      "comparablesMethod": {
        "value": 248000,
        "confidence": 78,
        "details": {
          "comparablesUsed": 12,
          "totalComparables": 45,
          "avgPricePerM2": 2920,
          "pricePerM2": 2882,
          "floorArea": 85,
          "totalFloorArea": 85,
          "range": {
            "low": 232000,
            "mid": 248000,
            "high": 264000,
            "spreadPct": 13,
            "p25PerM2": 2730,
            "p50PerM2": 2850,
            "p75PerM2": 3100
          }
        }
      }
    },
    "epc": {
      "currentEnergyRating": "D",
      "tenure": "Freehold",
      "propertyType": "House",
      "totalFloorArea": 85,
      "constructionAgeBand": "1950-1966"
    },
    "comparables": [ ... ]
  }
}

property

Subject property details including address, floor area, property type, and last sale information.

valuation

Valuation results with recommended value, range, and per-method breakdowns.

• recommended — the highest-confidence valuation with method name and confidence score
• range — low, mid, and high estimates combining both methods
• hpiMethod — valuation based on house price index movements (null if no previous sale found)
• comparablesMethod — valuation based on comparable sales analysis (null if no floor area data)

epc

Energy Performance Certificate data for the property (null if no EPC found).

comparables

Up to 20 nearby comparable property sales used in the valuation calculation.

The API uses standard HTTP status codes to indicate the success or failure of requests.

Error Response Example

{
  "success": false,
  "error": {
    "code": "VALUATION_NOT_POSSIBLE",
    "message": "Unable to produce a valuation. This may be because no previous sale or floor area data is available for this property.",
    "details": {
      "hpiError": "No previous sale found for this property",
      "comparablesError": "No floor area data available",
      "hpiDataAvailable": true,
      "comparablesAvailable": 23
    }
  }
}