Understanding EER & EER2: Energy Efficiency Ratings for HVAC Systems

When evaluating heating and cooling systems, energy efficiency is a key factor in both performance and cost savings. Two important metrics used in the HVAC industry are EER (Energy Efficiency Ratio) and EER2. Understanding these ratings can help homeowners and businesses choose systems that save energy, reduce utility bills, and comply with modern efficiency standards.

What is EER?

The Energy Efficiency Ratio (EER) measures the efficiency of an air conditioner or heat pump at a specific outdoor temperature, typically 95°F. It is calculated by dividing the cooling capacity (in BTUs per hour) by the electrical energy input (in watts):

EER = Cooling Capacity (BTU/hr) ÷ Power Input (Watts)

A higher EER indicates greater efficiency. For example, a system with an EER of 12 provides 12 BTUs of cooling for every watt of electricity consumed. EER is most useful for evaluating performance under peak load conditions, such as hot summer days.

What is EER2?

EER2 is a newer, more accurate efficiency metric introduced in 2023 as part of updated U.S. Department of Energy (DOE) standards. EER2 accounts for a range of operating conditions rather than a single test temperature, providing a better representation of a system’s real-world efficiency.

• More Accurate Measurement: EER2 adjusts the standard EER test to reflect typical summer temperature variations and energy usage patterns.
• Regulatory Compliance: As of 2025, new DOE and ENERGY STAR requirements for central air conditioners and heat pumps include minimum EER2 ratings.
• Comparison Tool: Consumers can use EER2 to compare the energy efficiency of systems more reliably than using EER alone.

Why EER & EER2 Matter

Both EER and EER2 are essential for evaluating HVAC systems, particularly in regions with hot climates or where air conditioning is used extensively:

• Energy Savings: Higher EER or EER2 ratings mean less electricity is used to cool your space.
• Lower Utility Bills: Efficient systems translate into measurable cost savings over time.
• Environmental Impact: Energy-efficient systems reduce greenhouse gas emissions and help meet sustainability goals.
• Incentives: Many states and utility companies offer rebates or tax credits for systems that meet or exceed minimum EER2 standards.

Understanding Current 2025 Standards

As of 2025, the DOE requires new central air conditioners and heat pumps to meet minimum efficiency levels using EER2:

• Split system central air conditioners: SEER2 ≥ 17.0, EER2 ≥ 12.0
• Heat pumps: SEER2 ≥ 17.0, EER2 ≥ 12.5

Systems meeting or exceeding these ratings qualify for ENERGY STAR certification and may be eligible for federal and local incentives.

How to Use EER & EER2 When Choosing a System

1. Check the Ratings: Look for the EER and EER2 values on the system’s specification sheet or ENERGY STAR label.
2. Compare Models: Higher ratings generally mean better efficiency, but consider installation costs and climate conditions.
3. Consult a Professional: A certified HVAC contractor can evaluate your home or building to recommend systems that balance efficiency, comfort, and cost.