Chapter 14: Energy Efficiency in HVAC
Energy efficiency is a critical goal in HVAC design, installation, and operation. Efficient systems reduce energy bills, environmental impact, and carbon footprint while ensuring comfort.
🔹 14.1 Why Energy Efficiency Matters in HVAC
💡 HVAC accounts for ~40–60% of energy use in buildings.
🌍 Helps in reducing greenhouse gas (GHG) emissions.💰 Reduces electricity bills.
🏢 Complies with energy codes (like ECBC, ASHRAE, IECC).
🏆 Required for certifications (LEED, IGBC, BEE Star).
🔹 14.2 Key Energy Efficiency Metrics
✅ EER – Energy Efficiency Ratio
Formula:
EER = Cooling Output (BTU/hr) ÷ Power Input (Watts)
Higher EER = more efficient
Example: 12,000 BTU/hr unit using 1,200 W → EER = 10Common in window ACs and small units
✅ SEER – Seasonal Energy Efficiency Ratio
SEER considers seasonal variation in temperature.
Formula:
SEER = Total seasonal cooling output (BTU) ÷ Total seasonal energy input (Watt-hours)
More realistic than EER
Commonly used in split ACs and residential HVACTypical SEER:
Old units: 8–10Newer units: 13–21+
India SEER guideline by BEE (Bureau of Energy Efficiency):
1-star: ~3.1
5-star: ~4.5+
✅ ISEER – Indian Seasonal Energy Efficiency Ratio
Introduced by BEE India for inverter ACs, considering India’s climate.
ISEER = Seasonal Cooling Output / Seasonal Power Input
More accurate for variable-speed systems
Considers India’s outdoor temperature profileNow mandatory for star-labeled inverter ACs
ERV (Energy Recovery Ventilator) recovers energy from exhaust air to pre-condition the incoming fresh air.
💡 How it works:
Incoming fresh air passes through a heat exchanger.
Extracts heat and humidity from outgoing air.Pre-heats in winter, pre-cools in summer.
✅ Benefits:
Reduces cooling/heating load.
Maintains indoor air quality.Ideal for tight buildings (where windows are sealed).
Saves up to 30% HVAC energy.
Some systems use HRV (Heat Recovery Ventilator) – similar but only exchanges heat, not humidity.
🔹 14.4 Green Building Concepts – LEED
LEED (Leadership in Energy and Environmental Design) is a globally recognized green building certification system by the U.S. Green Building Council (USGBC).
HVAC-related LEED strategies:
Use of energy-efficient equipment
Optimized HVAC design (low load, zoning)Use of ERVs, VAVs, and chillers with high COP
Building Energy Modeling (using software)
Proper commissioning and controls
LEED Certification Levels:
| Level | Points |
|---|---|
| Certified | 40–49 |
| Silver | 50–59 |
| Gold | 60–79 |
| Platinum | 80+ |
🛠️ Practical: Compare SEER Ratings of 3 AC Units
| Brand | Model | SEER / ISEER | Star Rating (India) |
|---|---|---|---|
| LG DualCool | JS-Q18HUZD | 4.73 (ISEER) | ★★★★★ |
| Voltas | 183V ADS | 3.8 (ISEER) | ★★★★☆ |
| Hitachi | RAU318HTD | 3.2 (EER) | ★★★☆☆ |
👉 Inference:
LG is most efficient but costliest.
Voltas offers a good balance.Hitachi consumes more energy for same cooling.
📄 Assignment/Interview Questions
✅ Q1: How does ERV save energy?
Answer:
ERV saves energy by recovering heat and moisture from the outgoing exhaust air and transferring it to incoming fresh air. This reduces the temperature difference that HVAC has to overcome, thereby reducing cooling/heating load by 20–30%, especially in climates with high ventilation requirements.
✅ Q2: What is a good EER value?
Answer:
A good EER value is typically 10 or above.
Modern energy-efficient systems may have EER values 12–14.In Indian standards, EER ≥ 3.5 (~12 BTU/W) is considered efficient.