A Model Context Protocol (MCP) server for residential heat pump sizing, cost estimation, and cold-climate performance verification. Use with AI assistants like Claude Desktop, Claude Code, Cursor, and other MCP clients.

Works out-of-the-box with bundled data - no API keys required!

The server runs directly via uvx - no installation required. Your MCP client will handle this automatically.

Choose your preferred AI assistant:

{
  "mcpServers": {
    "heatpump-calculator": {
      "command": "uvx",
      "args": ["--refresh", "--from", "git+https://github.com/subspace-lab/heatpump-mcp-server.git", "heatpump-mcp-server"]
    }
  }
}

{
  "mcpServers": {
    "heatpump-calculator": {
      "command": "uvx",
      "args": ["--refresh", "--from", "git+https://github.com/subspace-lab/heatpump-mcp-server.git", "heatpump-mcp-server"]
    }
  }
}

{
  "mcpServers": {
    "heatpump-calculator": {
      "command": "uvx",
      "args": ["--refresh", "--from", "git+https://github.com/subspace-lab/heatpump-mcp-server.git", "heatpump-mcp-server"]
    }
  }
}

{
  "mcpServers": {
    "heatpump-calculator": {
      "command": "uvx",
      "args": ["--refresh", "--from", "git+https://github.com/subspace-lab/heatpump-mcp-server.git", "heatpump-mcp-server"]
    }
  }
}

That's it! The server includes:

• 81 heat pump models from major manufacturers
• 2024 state-average electricity rates for all US states
• TMY3 weather station data for climate zones

No API keys needed to get started.

• calculate_heat_pump_sizing: Single-zone BTU sizing with humidity considerations
• calculate_multi_zone_sizing: Floor-by-floor load calculations for complex homes
• estimate_energy_costs: Bill comparison and 10-year payback analysis
• check_cold_climate_performance: Verify capacity at design temperature
• get_electricity_rate: Fetch current electricity rates by ZIP code
• list_heat_pump_models: Browse 81 heat pump models with specs

• design-temps/{zip_code}: Climate data and design temperatures
• heat-pump-models: Complete model database with BTU, HSPF2, prices
• climate-zones: ASHRAE climate zone reference

• size-heat-pump: Step-by-step sizing guidance
• analyze-costs: Cost comparison workflow
• verify-cold-climate: Cold climate suitability check

User: I need help sizing a heat pump for my 2000 sq ft home built in 1995 in ZIP 02138.

AI: [Uses calculate_heat_pump_sizing tool]
Based on your location (Cambridge, MA - Climate Zone 5A) and home characteristics:
- Required BTU: 80,000 BTU
- Recommended range: 72,000 - 88,000 BTU
- Design temperature: 6°F
...

User: What would a Mitsubishi MXZ-3C30NA cost to operate vs my gas furnace?

AI: [Uses estimate_energy_costs tool]
Annual cost comparison:
- Heat pump: $1,850/year (using bundled state average rate)
- Gas furnace: $2,400/year
- Annual savings: $550
- Payback period: 8.2 years
...

User: Will a Fujitsu AOU24RLXFZ work in Minneapolis?

AI: [Uses check_cold_climate_performance tool]
Cold climate analysis:
- Design temp: -13°F
- Heat pump capacity at design: 18,000 BTU
- Your heating load: 75,000 BTU
- Coverage: 24% (Inadequate)
- Recommendation: You'll need substantial backup heat...

For more accurate electricity rates, you can optionally provide an EIA API key:

1. Get a free EIA API key: https://www.eia.gov/opendata/register.php

2. Add to your MCP client config:

{
  "mcpServers": {
    "heatpump-calculator": {
      "command": "uvx",
      "args": ["--refresh", "--from", "git+https://github.com/subspace-lab/heatpump-mcp-server.git", "heatpump-mcp-server"],
      "env": {
        "EIA_API_KEY": "your_eia_api_key_here"
      }
    }
  }
}

Or create a .env file in your working directory:

# Optional: For live electricity rate lookups
EIA_API_KEY=your_eia_api_key_here

Note: Without an API key, the server uses 2024 state-average electricity rates, which are generally accurate for cost estimates.

git clone https://github.com/subspace-lab/heatpump-mcp-server.git
cd heatpump-mcp-server
uv pip install -e .

If you prefer to install the package locally instead of using uvx:

# Install from GitHub
uv pip install git+https://github.com/subspace-lab/heatpump-mcp-server.git

# Then configure your MCP client to use the local installation:
{
  "mcpServers": {
    "heatpump-calculator": {
      "command": "heatpump-mcp-server"
    }
  }
}

Note: Using uvx with --refresh is recommended for most users as it automatically updates to the latest version.

Built on FastMCP for easy MCP server development.

• Heat Pump Models: Bundled database of 81 models (Mitsubishi, Fujitsu, Daikin, LG, etc.)
• Climate Data: TMY3 weather station database with design temperatures
• Electricity Rates: Bundled 2024 state averages (EIA API optional for live data)

• Sizing: Climate-zone specific BTU/sqft coefficients based on building age and insulation
• Costs: Monthly degree-day analysis with heat pump COP curves
• Cold Climate: Manufacturer capacity curves with temperature derating

# Clone repo
git clone https://github.com/subspace-lab/heatpump-mcp-server.git
cd heatpump-mcp-server

# Install with dev dependencies
uv pip install -e ".[dev]"

# Run tests
pytest

# Lint code
ruff check .

heatpump_mcp_server/
├── src/heatpump_mcp_server/
│   ├── server.py          # Main MCP server
│   ├── tools.py           # Calculator tools
│   ├── resources.py       # Data resources
│   ├── prompts.py         # Guided prompts
│   ├── config.py          # Configuration
│   ├── models/            # Pydantic models
│   └── services/          # Business logic
│       ├── quick_sizer_service.py
│       ├── bill_estimator_service.py
│       ├── cold_climate_service.py
│       └── ...
├── data/                  # Bundled data files
│   ├── hpmodels.json      # 81 heat pump models
│   └── eeweather_stations.json  # Weather data
├── tests/
├── pyproject.toml
└── README.md

Contributions welcome! Areas for improvement:

• Additional heat pump models
• More weather stations for better coverage
• Manual J load calculation support
• International climate zone support

MIT License - see LICENSE file for details.

• Climate data from EEWeather
• Heat pump specs compiled from manufacturer data
• Built with FastMCP
• Electricity rate fallbacks from EIA

• Issues: https://github.com/subspace-lab/heatpump-mcp-server/issues
• Discussions: https://github.com/subspace-lab/heatpump-mcp-server/discussions