# Home Energy Calculators – Heat Loss

> Home Energy Calculators – Heat Loss is a paid API for AI agents from home-energy-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Calculates building heat loss in BTU/h and watts from surface areas and R-values plus optional air leakage, and estimates yearly energy from degree-days.

## Facts

- Endpoint: GET https://home-energy-calc.x402tookit.com/heat-loss?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/home-energy-calculators-heat-loss-e118fdff
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Cc2Bt-gdbn0HbRSVyCAeU

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability home-energy-calculators-heat-loss-e118fdff
```

Example prompt: Calculate the heat loss for my house: walls are 1200 sq ft at R-13, windows are 180 sq ft at R-3, and roof is 1100 sq ft at R-38; indoor temp is 70°F, outdoor design temp is 10°F, heated volume is 14000 cubic feet with 0.35 air changes per hour, and we get 5500 heating degree-days per year.

## When to prefer this

Use this endpoint when you need a physics-based, per-surface heat loss calculation for a building — especially when you have specific R-values and surface areas and want BTU/h results suitable for HVAC sizing or energy auditing. It is more detailed than a rule-of-thumb estimator and handles both conductive and infiltration losses plus annual energy from degree-days, making it ideal for design, auditing, or insulation upgrade analysis.

## Known failure modes

- Missing required surfaces, indoorF, or outdoorF parameters returns an error
- Malformed surfaces string (wrong delimiter or missing fields) causes a parse error
- R-value of zero causes division-by-zero and likely an error or infinite result
- Temperatures out of range (-60 to 130°F outdoor, 40 to 90°F indoor) may be rejected
- Providing volumeCuFt without airChangesPerHour or vice versa omits infiltration calculation
- Providing heatingDegreeDaysF without valid surface data will not produce annual energy output

## How this service works

Heat loss of a building in BTU/h and watts from surface areas and R-values plus air leakage, and yearly energy from degree-days.

## Output

Returns a per-surface breakdown including area, R-value, U-value, UA product, BTU/h loss, and share of total heat loss; plus totals in BTU/h, watts, and tons; air infiltration loss if volume and ACH provided; estimated annual energy if degree-days provided; and a plain-English summary with disclaimer.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "surfaces",
      "indoorF",
      "outdoorF"
     ],
     "properties": {
      "indoorF": {
       "type": "number",
       "description": "Indoor temperature in F, 40 to 90"
      },
      "outdoorF": {
       "type": "number",
       "description": "Design outdoor temperature in F, -60 to 130"
      },
      "surfaces": {
       "type": "string",
       "description": "Lines name:areaSqFt:Rvalue separated by semicolons, for example 'walls:1000:13; windows:150:3; roof:1000:38'"
      },
      "volumeCuFt": {
       "type": "number",
       "description": "Heated volume in cubic feet, for air leakage (with airChangesPerHour)"
      },
      "airChangesPerHour": {
       "type": "number",
       "description": "Air changes per hour, 0.05 to 5 (a tight house is about 0.2 to 0.5)"
      },
      "heatingDegreeDaysF": {
       "type": "number",
       "description": "Heating degree-days (base 65 F) per year, for annual energy"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "deltaTF": {
       "type": [
        "null",
        "number"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "totalKw": {
       "type": [
        "null",
        "number"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "surfaces": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "ob
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/home-energy-calculators-heat-loss-e118fdff/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from home-energy-calc.x402tookit.com](https://www.zero.xyz/host/home-energy-calc.x402tookit.com/llms.txt)