Residential HVAC Performance Baseline

A Five-Year Longitudinal Study of High-Efficiency Residential Energy Systems in Climate Zone 5A

DOI Version License: MIT Home Assistant Climate Zone Data Period

Overview

This repository documents a comprehensive energy performance baseline for a 2,440 sq. ft. high-efficiency residential structure in Central Connecticut (Climate Zone 5A). The analysis integrates 50 months of verified utility data (January 2022 - February 2026), high-resolution HVAC runtime telemetry, and independent domestic hot water monitoring to establish diagnostic performance thresholds.

Key Findings (Updated February 2026):

πŸ†• February 2026 Update Highlights

February 2026 continued the colder-than-normal 2025-2026 heating season, with an early-month cold snap (Feb 7-9) reaching 0Β°F:

Metric Feb 2025 Feb 2026 YoY Change Status
Total Gas 154 CCF 175 CCF +13.6% βœ… Weather-driven
Space Heating 135.9 CCF 160.9 CCF +18.4% βœ… Tracks weather
DHW (Navien) 18.1 CCF 14.1 CCF -22.0% βœ… Savings hold
Weather Severity 940 HDD 1,077 HDD +14.6% ⚠️ Colder
HVAC Runtime 138 hrs 158 hrs (8.8 min/HDD) +14.5% βœ… Excellent

Key Insights:

  1. DHW savings sustained: -22% YoY continues from January optimization
  2. Runtime efficiency excellent: 8.8 min/HDD is 19% better than baseline
  3. Season totals: 720 heating hours across 4,529 HDD (Oct-Feb)

DHW Recirculation Optimization (Ongoing)

Cumulative Savings (Jan-Feb 2026): 9.05 CCF (~$14.50) On Track For: ~$77/year projected annual savings Schedule: 15 hr/day (off 9 PM - 6 AM) β€” no comfort issues reported

See FEBRUARY_2026_UPDATE.md for complete analysis. See JANUARY_2026_UPDATE.md for DHW optimization details.

πŸ—οΈ System Architecture

flowchart TB
    subgraph inputs["πŸ“‘ Data Sources"]
        T1["🌑️ 1F Thermostat<br/>Honeywell T6 Pro"]
        T2["🌑️ 2F Thermostat<br/>Honeywell T6 Pro"]
        PW["🌀️ Pirate Weather API"]
        OM["🌀️ Open-Meteo API"]
        CN["πŸ“Š Climate Norms<br/>18-year historical"]
    end

    subgraph ha["🏠 Home Assistant Core"]
        direction TB
        RT["Runtime Tracking<br/>β€’ 1F/2F heat cycles<br/>β€’ Furnace runtime<br/>β€’ Zone overlap"]
        DD["Degree Day Calc<br/>β€’ HDD65/CDD65<br/>β€’ 7-day rolling<br/>β€’ Monthly cumulative"]
        SPC["Statistical Process Control<br/>β€’ Rolling mean Β± 2Οƒ<br/>β€’ Anomaly detection<br/>β€’ Control charts"]
        REC["Recovery Analysis<br/>β€’ Setback recovery time<br/>β€’ Weather-adjusted rates<br/>β€’ Per-zone tracking"]
    end

    subgraph outputs["πŸ“€ Outputs"]
        CSV["πŸ“ CSV Reports<br/>Daily + Monthly"]
        ALERT["🚨 Alerts<br/>Efficiency deviation<br/>Filter replacement"]
        DASH["πŸ“Š Dashboards<br/>ApexCharts + Mushroom"]
        GH["πŸ™ GitHub Archive"]
    end

    T1 --> RT
    T2 --> RT
    PW --> DD
    OM --> DD
    CN --> SPC
    RT --> SPC
    DD --> SPC
    RT --> REC
    
    SPC --> CSV
    SPC --> ALERT
    SPC --> DASH
    CSV --> GH

🎯 What Makes This Different

Traditional Monitoring This Approach
β€œYour furnace ran 4 hours today” β€œYour furnace ran 12% more than expected for today’s weather”
Static efficiency thresholds Rolling Β±2Οƒ control limits that adapt to your home
Single-zone analysis Chaining Index quantifies multi-zone coordination
Compare to yesterday Compare to 18-year climate normals for this date
Equipment-focused Post-Program Efficiency framework for already-efficient homes

πŸ“Š Five-Year Performance Summary

Metric 2022 2023 2024 2025 2026 YTD
Annual Gas (CCF) 815 764 694 787 343*
Annual Elec (kWh) 6,824 6,591 6,543 6,730 919*
Heating Intensity 89.8 90.8 80.3 95.5 135.0*
Site EUI 42.1 40.8 38.2 41.7 β€”

*Jan-Feb 2026 only (partial year)

Statistical Stability (4-Year Baseline)

Metric Mean Std Dev CV (%) Status
Heating Intensity (CCF/1k HDD) 89.1 6.2 7.0% βœ… Excellent
Site EUI (kBTU/ftΒ²-yr) 40.8 2.1 5.1% βœ… Excellent
Electricity Baseload 9.6 kWh/day 0.3 3.1% βœ… Exceptional

πŸš€ Quick Start (Home Assistant Users)

For the full Home Assistant configuration that powers the sensors, dashboards, and automation used to generate this dataset, see the companion repo: wkcollis1-eng/home-assistant-config.

curl -o /config/packages/hvac_baseline.yaml \
  https://raw.githubusercontent.com/wkcollis1-eng/Residential-HVAC-Performance-Baseline-/main/homeassistant/packages/hvac_baseline.yaml

Option 2: Core Sensor (5 minutes)

The single most useful efficiency metric: 

template:
  - sensor:
      - name: "HVAC Runtime per HDD Today"
        unique_id: hvac_runtime_per_hdd_today
        unit_of_measurement: "min/HDD"
        state: >
          {% set runtime_hours = states('sensor.YOUR_HEAT_RUNTIME_TODAY') | float(0) %}
          {% set outdoor_mean = (states('sensor.YOUR_OUTDOOR_HIGH') | float(0) + 
                                 states('sensor.YOUR_OUTDOOR_LOW') | float(0)) / 2 %}
          {% set hdd = [65 - outdoor_mean, 0] | max %}
          {{ ((runtime_hours * 60) / hdd) | round(1) if hdd > 0 else 0 }}

πŸ“ Repository Structure

β”œβ”€β”€ README.md                     # This file
β”œβ”€β”€ BASELINE_REPORT.md            # Complete technical analysis (17,000+ words)
β”œβ”€β”€ DATA_SUMMARY.md               # Quick-reference metrics and tables
β”œβ”€β”€ METHODOLOGY.md                # Billing-aligned calculation methodology
β”œβ”€β”€ SYSTEM_SPECIFICATIONS.md      # Equipment technical specifications
β”œβ”€β”€ JANUARY_2026_UPDATE.md        # January 2026 performance analysis
β”œβ”€β”€ FEBRUARY_2026_UPDATE.md       # πŸ†• February 2026 performance analysis
β”œβ”€β”€ REALTIME_MONITORING_2026.md   # Home Assistant implementation details
β”œβ”€β”€ homeassistant/                # Home Assistant configuration
β”‚   β”œβ”€β”€ packages/
β”‚   β”‚   └── hvac_baseline.yaml
β”‚   └── dashboards/
└── data/                         # Raw operational datasets
    β”œβ”€β”€ daily_temperature.csv     # πŸ†• Updated through Feb 2026
    β”œβ”€β”€ monthly_hvac_runtime.csv  # πŸ†• Updated through Feb 2026
    β”œβ”€β”€ monthly_dhw_navien.csv    # πŸ†• Updated through Feb 2026
    β”œβ”€β”€ monthly_electricity_eversource.csv
    └── monthly_gas_scg.csv

🏠 Property Context

Attribute Specification
Location Central Connecticut, Climate Zone 5A
Construction 2021, Two-story Colonial
Conditioned Area 2,440 sq. ft.
Occupancy 2 residents
Primary Heating American Standard Silver 95 (96% AFUE) condensing gas furnace
Primary Cooling American Standard Silver 14 (4-ton, 14 SEER) split system
Zoning 2-zone (1F/2F) with Honeywell T6 Pro thermostats
Moisture Control Santa Fe Classic dehumidifier (110 PPD, 700W)
DHW Navien NPE-series condensing tankless

πŸ“ˆ Investigation Thresholds (2026)

Metric Baseline Warning (+10%) Action (+15%)
Heating Intensity 90.3 CCF/1k HDD >99 >104
Runtime Efficiency 10.9 min/HDD >12.0 >12.5
Monthly Space Heat (Jan) 138 CCF >152 >159
Monthly DHW (Jan) 22.8 CCF >25.1 >26.2
Zone Imbalance 50% Β±5% <42% or >58% <38% or >62%

Live Monitoring Implementation

The baseline analysis feeds into a real-time Home Assistant monitoring system that tracks performance against established thresholds using Statistical Process Control (SPC). This implementation demonstrates how the calculated baselines translate into operational anomaly detection.

Dashboard Overview

The monitoring system provides continuous validation of system performance:

Performance Gauges Real-time performance tracking against baseline targets with color-coded status indicators

Efficiency Tracking Statistical Process Control monitoring showing 7-day rolling means and Β±2Οƒ bounds derived from baseline analysis

System Alerts Automated health checks ensuring data capture integrity and alerting on efficiency degradation

Key Monitoring Features

Full monitoring configuration and implementation details:
πŸ“‚ home-assistant-config

For additional dashboard views and implementation notes, see DASHBOARD_EXAMPLES.md.

⚠️ Why Standard Utility Programs Don’t Apply

This home’s exceptional performance (41.7 kBTU/ftΒ²-yr EUI, 33% better than regional average) places it beyond the design envelope of traditional utility efficiency programs.

Key Finding: Standard interventions (insulation upgrades, equipment replacement) would yield <5% additional savings at costs exceeding 20-year payback periods.

See UTILITY_PROGRAM_ANALYSIS.md for detailed analysis.

πŸ“¬ Recent Updates

v1.4.0 (March 2026)

v1.3.2 (February 2026)

v1.2.1 (January 2026)

πŸ“š Citation

@misc{collis2026hvac,
  author = {Collis, William K.},
  title = {Residential HVAC Performance Baseline: A Five-Year Longitudinal Study in Climate Zone 5A},
  year = {2026},
  publisher = {GitHub},
  url = {https://github.com/wkcollis1-eng/Residential-HVAC-Performance-Baseline-},
  doi = {10.5281/zenodo.18232616}
}

🀝 Contributing

Contributions welcome! Particularly interested in:

See CONTRIBUTING.md for guidelines.

πŸ“¬ Contact

Version: 1.4.0 (March 2026) Status: Active Baseline β€” 50 months of validated data Next Update: April 2026 (post-winter season summary)