The Energy Efficiency Ratio (EER) is a measure of how efficiently a cooling system converts electrical energy into cooling capacity under a specific set of operating conditions. It is defined as the ratio of cooling output in BTU/h to power input in watts: EER = BTU/h output / Watts input. A higher EER indicates greater energy efficiency — a system with EER 14 uses less electricity to produce the same cooling as one with EER 10. EER is tested at a fixed standard condition: 95°F outdoor dry-bulb temperature, 80°F indoor dry-bulb, 67°F indoor wet-bulb. These conditions represent a hot summer peak. By contrast, SEER (Seasonal Energy Efficiency Ratio) represents average efficiency over an entire cooling season with varying temperatures and is typically higher than EER for the same unit because real seasons include many mild days. SEER2 (introduced 2023) uses updated test procedures with more realistic duct static pressures. For heating, heat pumps use COP (Coefficient of Performance) or HSPF (Heating Seasonal Performance Factor): HSPF = Total seasonal BTU heating / Total seasonal watt-hours consumed. A heat pump with HSPF 10 provides 10 BTU of heat per watt-hour, compared to electric resistance heating at exactly 1 BTU/watt-hour (3.412 BTU/watt-hour × 1 = 3.412 HSPF equivalent, or COP 1.0). For commercial systems, IEER (Integrated EER) or IPLV (Integrated Part Load Value) better represent real-world performance by weighting efficiency at 100%, 75%, 50%, and 25% of rated capacity — reflecting that systems rarely operate at full load. DOE minimum standards: as of 2023, residential central AC must meet 14 SEER2 (North) or 15 SEER2 (South/Southwest). High-efficiency units reach 20–26 SEER2. ENERGY STAR requires ≥15 SEER2 / ≥12.5 EER2.
EER = Cooling capacity (BTU/h) / Power input (Watts) SEER = Total seasonal BTU cooling / Total seasonal Watt-hours
- 1Gather the required input values: EER, SEER, SEER2, COP.
- 2Apply the core formula: EER = Cooling capacity (BTU/h) / Power input (Watts) SEER = Total seasonal BTU cooling / Total seasonal Watt-hours.
- 3Compute intermediate values such as COP_cooling if applicable.
- 4Verify that all units are consistent before combining terms.
- 5Calculate the final result and review it for reasonableness.
- 6Check whether any special cases or boundary conditions apply to your inputs.
- 7Interpret the result in context and compare with reference values if available.
Primary care physicians and internists use Energy Efficiency Ratio during routine clinical assessments to screen patients, establish baselines for longitudinal monitoring, and identify individuals who may need referral to specialists for further diagnostic evaluation or therapeutic intervention.
Hospital clinical pharmacists apply Energy Efficiency Ratio to verify drug dosing calculations, particularly for medications with narrow therapeutic indices like warfarin, aminoglycosides, and chemotherapy agents where patient-specific factors such as renal function and body weight critically affect safe dosing ranges.
Public health epidemiologists use Energy Efficiency Ratio in population-level screening programs to calculate disease prevalence, assess screening test sensitivity and specificity, and determine the number needed to screen to detect one case in various demographic subgroups.
Clinical researchers incorporate Energy Efficiency Ratio into study design protocols to calculate sample sizes, determine statistical power for detecting clinically meaningful differences, and establish inclusion criteria based on quantitative physiological thresholds.
Pediatric versus adult reference ranges
In practice, this edge case requires careful consideration because standard assumptions may not hold. When encountering this scenario in energy efficiency ratio calculations, practitioners should verify boundary conditions, check for division-by-zero risks, and consider whether the model's assumptions remain valid under these extreme conditions.
Pregnancy and hormonal variations
In practice, this edge case requires careful consideration because standard assumptions may not hold. When encountering this scenario in energy efficiency ratio calculations, practitioners should verify boundary conditions, check for division-by-zero risks, and consider whether the model's assumptions remain valid under these extreme conditions.
Extreme body composition
In practice, this edge case requires careful consideration because standard assumptions may not hold. When encountering this scenario in energy efficiency ratio calculations, practitioners should verify boundary conditions, check for division-by-zero risks, and consider whether the model's assumptions remain valid under these extreme conditions.
| Metric | Value Range | Meaning | Equipment Type |
|---|---|---|---|
| SEER2 | 14–26 | Seasonal cooling efficiency | Central AC, heat pump |
| EER | 8–14 | Peak cooling efficiency | All cooling systems |
| HSPF2 | 7–11 | Seasonal heating efficiency | Heat pumps |
| COP (heating) | 1.5–4.5 | Instantaneous heating efficiency | Heat pumps |
| AFUE | 80–98.5% | Annual heating fuel efficiency | Gas/oil furnaces |
| IPLV | 0.30–0.60 kW/ton | Part-load chiller efficiency | Centrifugal chillers |
In the context of Energy Efficiency Ratio, this depends on the specific inputs, assumptions, and goals of the user. The underlying formula provides a deterministic relationship between inputs and output, but real-world application requires interpreting the result within the broader context of health and medical practice. Professionals typically cross-reference calculator output with industry benchmarks, historical data, and regulatory requirements. For the most reliable results, ensure inputs are sourced from verified data, understand which assumptions the formula makes, and consider running multiple scenarios to bracket the range of likely outcomes.
In the context of Energy Efficiency Ratio, this depends on the specific inputs, assumptions, and goals of the user. The underlying formula provides a deterministic relationship between inputs and output, but real-world application requires interpreting the result within the broader context of health and medical practice. Professionals typically cross-reference calculator output with industry benchmarks, historical data, and regulatory requirements. For the most reliable results, ensure inputs are sourced from verified data, understand which assumptions the formula makes, and consider running multiple scenarios to bracket the range of likely outcomes.
In the context of Energy Efficiency Ratio, this depends on the specific inputs, assumptions, and goals of the user. The underlying formula provides a deterministic relationship between inputs and output, but real-world application requires interpreting the result within the broader context of health and medical practice. Professionals typically cross-reference calculator output with industry benchmarks, historical data, and regulatory requirements. For the most reliable results, ensure inputs are sourced from verified data, understand which assumptions the formula makes, and consider running multiple scenarios to bracket the range of likely outcomes.
In the context of Energy Efficiency Ratio, this depends on the specific inputs, assumptions, and goals of the user. The underlying formula provides a deterministic relationship between inputs and output, but real-world application requires interpreting the result within the broader context of health and medical practice. Professionals typically cross-reference calculator output with industry benchmarks, historical data, and regulatory requirements. For the most reliable results, ensure inputs are sourced from verified data, understand which assumptions the formula makes, and consider running multiple scenarios to bracket the range of likely outcomes.
In the context of Energy Efficiency Ratio, this depends on the specific inputs, assumptions, and goals of the user. The underlying formula provides a deterministic relationship between inputs and output, but real-world application requires interpreting the result within the broader context of health and medical practice. Professionals typically cross-reference calculator output with industry benchmarks, historical data, and regulatory requirements. For the most reliable results, ensure inputs are sourced from verified data, understand which assumptions the formula makes, and consider running multiple scenarios to bracket the range of likely outcomes.
In the context of Energy Efficiency Ratio, this depends on the specific inputs, assumptions, and goals of the user. The underlying formula provides a deterministic relationship between inputs and output, but real-world application requires interpreting the result within the broader context of health and medical practice. Professionals typically cross-reference calculator output with industry benchmarks, historical data, and regulatory requirements. For the most reliable results, ensure inputs are sourced from verified data, understand which assumptions the formula makes, and consider running multiple scenarios to bracket the range of likely outcomes.
In the context of Energy Efficiency Ratio, this depends on the specific inputs, assumptions, and goals of the user. The underlying formula provides a deterministic relationship between inputs and output, but real-world application requires interpreting the result within the broader context of health and medical practice. Professionals typically cross-reference calculator output with industry benchmarks, historical data, and regulatory requirements. For the most reliable results, ensure inputs are sourced from verified data, understand which assumptions the formula makes, and consider running multiple scenarios to bracket the range of likely outcomes.
Pro Tip
To maximize realized efficiency, correct refrigerant charge, clean coils, and proper airflow are worth 10–15% efficiency improvement before any equipment upgrade. Maintain first, then upgrade.
Did you know?
The first room air conditioner sold commercially in 1939 (the Carrier Weathermaker) had an EER of about 5. Today's minimum-standard window units achieve EER 10 — double the efficiency of the first units — and the best systems are 4–5× more efficient.