Energy Efficient Buildings - Rating Systems

Energy Efficiency Certifications, Labels and Ratings

The economic and environmental benefits of energy efficiency are evident, but identifying the most efficient products and equipment can be a challenge. There is no single metric that you can apply to all energy-consuming devices; for example, LED lamps and mini-split air conditioners have very different functions and operating principles.

Governments, research institutions and industry associations have created useful metrics to describe the energy performance of many product categories, and even buildings. For instance, you can look for appliances with the ENERGY STAR logo: these have been tested successfully under stringent standards, in laboratories that are completely independent from manufacturers.

Here we will review several energy efficiency certifications, product labels and ratings you will encounter in the market. By understanding how each of them works, you can compare products more effectively and make better purchase decisions.

ENERGY STAR Program: Building Certifications

The ENERGY STAR program is not limited to specific appliances and equipment. You can also certify an entire building, as long your occupancy classification is eligible and the property meets their performance criteria.

  • To certify a commercial building, first you need to calculate its ENERGY STAR score with the Portfolio Manager tool provided by the EPA.
  • Your building will get a score from 1 to 100, based on how it performs compared with other properties of the same type.
  • If your building gets a score of at least 75, it becomes ENERGY STAR Certified. These scores are recalculated each year, and your building must stay at 75 or above to keep the certification.
  • The building information must be submitted by a licensed Professional Engineer (PE) or Registered Architect (RA).

Keep in mind that the ENERGY STAR Score is based on percentiles. This means a building with a score above 90 is among the top 10% most efficient buildings of its type. Also consider that buildings are only compared with similar properties; this means an office building will only be compared with other commercial offices, and not with schools or healthcare buildings.

You can use the Portfolio Manager for more than 80 building categories. 21 of them are eligible for an ENERGY STAR score, and 17 of these 21 types are eligible for certification.

Eligibility  Property Types
ENERGY STAR Score and Certification Bank branch


Data center

Distribution center

Financial office

Hospital (general medical & surgical)


K-12 school

Multifamily housing

Non-refrigerated warehouse


Refrigerated warehouse

Retail store

Senior living community

Supermarket/grocery store

Wholesale club/ supercenter

Worship facility 

ENERGY STAR Score only Barracks

Medical office

Residence hall/ dormitory

Wastewater treatment plant

The ENERGY STAR Certification can greatly increase the value of your building, and it provides a major marketing advantage for real estate companies. Certified buildings are more appealing for potential tenants, since they have reduced energy costs.

The DesignLights Consortium Label (DLC)

Unlike ENERGY STAR, which covers many product categories and building types, the DLC label is exclusively for commercial and industrial lighting. However, the label is very helpful when comparing lighting options for these building types.

You can check the DLC Qualified Products List to find the most efficient light fixtures for commercial and industrial applications. The list is also useful for validating DLC labels on lighting products before your purchase.

Comparing the ENERGY STAR and DLC Labels

You will notice that some lighting products have ENERGY STAR labels, others have DLC labels, but there are no products with both. You might ask yourself if one label is better than the other, but they are mutually exclusive:

  • ENERGY STAR tends to focus on residential products, while DLC focuses on commercial and industrial lighting.
  • The US EPA is a government agency, while DesignLights Consortium is an industry association. For this reason, ENERGY STAR has priority over DLC when a product is eligible for both labels.

Energy rebate programs that cover lighting upgrades will normally require the ENERGY STAR or DLC label, or a similar certification. Program managers want to ensure that their incentives are used for high-quality lamps and fixtures, and looking for labeled products is a quick solution.

Energy Efficiency Ratings for Heating and Cooling Equipment

Space heating and air conditioning are the top energy expenses in most residential and commercial buildings, and they are only surpassed by manufacturing equipment in most industrial settings. Since there are many types of heating and cooling equipment, research institutions and industry associations have developed specific metrics for each. In fact, the ENERGY STAR program uses these performance ratings as part of their technical requirements for many HVAC products.

For example, you cannot compare an air-source heat pump directly with a furnace in terms of efficiency, since their operating principles and energy inputs are completely different. You can compare their ownership costs, but you need a unique rating to describe the energy performance of each equipment type.

Here we will provide an overview of some common efficiency ratings for HVAC equipment. Unlike ENERGY STAR and DLC, which are labeling programs, these metrics can be compared with gas mileage of a car (heating or cooling achieved, per unit of energy consumed).

EER: Energy Efficiency Ratio

The EER is an energy efficiency metric for cooling equipment, which indicates the British Thermal Units (BTU) of cooling for every watt-hour of electricity consumed. The EER is determined under specific operating conditions:

  • An outdoor temperature of 95°F
  • An indoor temperature of 80°F
  • 50% relative humidity

If you find an air conditioner with an energy efficiency ratio (EER) of 12, it provides 12 BTU of cooling for every watt-hour of electricity, under the operating conditions described above. Considering kilowatt-hours, the energy units used in your power bills, this air conditioner has a cooling performance of 12,000 BTU per kWh.

The EER is a simple concept, but it has a technical limitation. The ratio only considers a specific operating condition (95°F outdoors, 80°F indoors, 50% relative humidity), and air conditioners are subject to various temperatures and humidity levels throughout the year. When you want to compare the performance of air conditioners under changing weather conditions, the Seasonal Energy Efficiency Ratio or SEER is a more useful metric.

SEER: Seasonal Energy Efficiency Ratio

The SEER is used to describe the energy performance of unitary air conditioners, and also air-source heat pumps (ASHPs) in cooling mode. This ratio describes energy performance throughout the entire cooling season, and it indicates BTU of cooling for every watt-hour of consumption. Compared with the EER, the SEER provides a better picture of energy efficiency, since it considers the entire cooling season instead of a single operating point.

  • For example, if an air conditioner has a SEER of 16, it provides 16 BTU of cooling per watt-hour consumed. This is equivalent to 16,000 BTU per kilowatt-hour.
  • On the other hand, a SEER 28 unit would be providing 28,000 BTU per kWh.

Just like a higher gas mileage (MPG) reduces fuel consumption, a higher SEER reduces the energy cost of air conditioning. In this case, the SEER 28 unit uses around 43% less electricity than the SEER 16 unit (assuming similar operating conditions). The SEER 16 unit must use 62.5 kWh to provide 1,000,000 BTU of cooling, while the SEER 28 unit only needs 35.7 kWh under the same workload.

The ENERGY STAR program establishes a minimum SEER of 15 for air conditioners and ASHPs with a cooling capacity below 65,000 BTU/h.

HSPF: Heating Seasonal Performance Factor

The HSPF is similar to the SEER, describing the energy performance of unitary air-source heat pumps during the heating season. In the case of reversible heat pumps, you will notice that the HSPF is lower than the SEER, since they are more efficient in cooling mode.

  • For example, an air-source heat pump with an HSPF of 10 delivers 10 BTU of heating per watt-hour consumed (10,000 BTU per kWh).
  • The ENERGY STAR program requires a minimum HSPF of 8.5 for air source heat pumps with a split configuration, and 8.2 HSPF for packaged units.

AFUE: Annual Fuel Utilization Efficiency

As implied by its name, this energy efficiency metric is used for fuel-burning equipment such as furnaces and boilers. The AFUE indicates the percentage of combustion energy that gets converted into a useful heating output. Older combustion heaters tend to have AFUE values below 70 or even below 60, while modern and efficient heaters have a typical AFUE above 90. The most efficient combustion heaters offer an AFUE above 95.

The ENERGY STAR program requires a minimum AFUE of 85% for oil-fired furnaces, 90% for gas-fired furnaces in the US South, and 95% for gas-fired furnaces in the US North. Their website provides a list of states considered in each of the two regions. In the case of boilers, the program requires a minimum AFUE of 87% for oil-fired units, and 90% for gas-fired units.

CEER: Combined Energy Efficiency Ratio

The CEER is used for window-type air conditioners, which are not covered by the SEER. To calculate the CEER, the average cooling output in BTU/hour is divided by the average electricity input in watts, considering both the compressor runtime and standby/off-mode consumption.

  • To qualify for the ENERGY STAR label, room air conditioners must meet a minimum CEER. The required value depends on their cooling capacity and design (without reverse cycle, with reverse cycle, and casement units).
  • Depending on these factors, the minimum CEER ranges from 9.9 to 12.1.
  • Window air conditioners must have energy saving mode to qualify for ENERGY STAR.

Packaged terminal air conditioners (PTAC) and portable air conditioners are not eligible for the ENERGY STAR, regardless of their CEER value.

IEER: Integrated Energy Efficiency Ratio

The IEER is used for commercial unitary air conditioners and heat pumps. This metric is a weighted average of energy performance under different workloads:

  • Operating at 100% load and 95.0°F ambient temperature, 2% of the time.
  • 75% load at 81.5°F ambient temperature, 61.7% of the time.
  • 50% load at 68.0°F ambient temperature, 23.8% of the time.
  • 25% load at 65.0°F ambient temperature, 12.5% of the time.

The ENERGY STAR program uses the SEER as a performance metric for cooling equipment below 65,000 BTU/h, and the IEER for larger equipment up to 240,000 BTU/h. The following table summarizes the requirements for central air conditioners and air-source heat pumps with a cooling capacity of 65,000 BTU/h or above.

Equipment Type Cooling Capacity Minimum IEER
Central air conditioner (cooling only) 65,000 BTU/h or above, less than 240,000 BTU/h 11.8
Central air conditioner with resistance heater 65,000 BTU/h or above, less than 240,000 BTU/h 11.8
Central air conditioner, all other heating types 65,000 BTU/h or above, less than 240,000 BTU/h 11.6
Air-source heat pump 65,000 BTU/h or above, less than 135,000 BTU/h 11.4
Air-source heat pump 135,000 BTU/h or above, less than 240,000 BTU/h 11

COP: Coefficient of Performance

The COP is a thermodynamics concept that describes both heating and cooling efficiency, regardless of the energy input. This means you can use the COP for devices that use electricity, natural gas, heating oil, propane, etc. In simple terms, the COP is the heating or cooling output per energy unit consumed. This may sound similar to the SEER and HSPF, but there is an important difference:

  • The EER, SEER and HSPF consider a heating or cooling output measured in BTU, and an input in watt-hours.
  • To calculate the COP, the output and input must use the same energy units.

As a quick example, assume an air-source heat pump provides 9,500 BTU of heating for every kilowatt-hour consumed. To calculate the COP, you need to convert the heating output from BTU to kWh, or the energy input from kWh to BTU. 

Kilowatt-hours are normally used to measure electricity, but they can be used to describe any type of energy transfer, and this includes heating and cooling. One kilowatt-hour is equivalent to around 3,412 BTU, which means 9,500 BTU is roughly equivalent to 2.78 kWh.

  • Heating output in kWh = 9,500 BTU / 3,412 BTU per kWh = 2.78 kWh
  • COP = Heating output / electricity input = 2.78 kWh / 1 kWh = 2.78

The COP is unitless quantity, since it divides amounts of energy that are measured in the same units. When the COP is calculated, the energy measurement units cancel out.

NEMA Premium Efficiency

NEMA stands for National Electrical Manufacturers Association, a leading organization with more than 700 standards and technical documents published, and international recognition. They also created the NEMA Premium program, which has the goal of improving the efficiency of electric motors and transformers.

According to the International Energy Agency (IEA), electric motors and the equipment they drive represent 40% of global electricity consumption. Transformers are static devices, on the other hand, but many of them operate 24/7. They have variable losses that depend on their load, but also fixed losses that are always present. In a facility with many transformers, even a minor efficiency gain can save thousands of dollars per year.

Building owners can achieve major energy savings by replacing their motors and transformers with NEMA Premium Efficiency units:

  • NEMA Premium motors have the potential to save 5,800 gigawatts of electricity with widespread adoption. This would prevent 80 million metric tons of carbon dioxide emissions, equivalent to removing 16 million cars from the road.
  • NEMA Premium transformers can often reduce losses by 20% or more when replacing an equivalent transformer built according to the previous standard (NEMA TP-1).

You can find NEMA Premium Efficiency motors ranging from 1 hp to 500 hp. The program covers open drip-proof (ODP) and totally enclosed fan-cooled (TEFC) motors having 6-pole, 4-pole and 2-pole designs. This means you can find NEMA Premium motors for a wide range of commercial and industrial applications.

In 2016, the US Department of Energy introduced mandatory efficiency requirements for low-voltage dry-type transformers, based on NEMA standards. These requirements cover transformers ranging from 15 kVA to 1000 kVA, and the minimum efficiency depends on the nameplate capacity.

For example, the older NEMA TP-1 standard requires 98.0% efficiency for a 75 kVA transformer (low-voltage, dry-type), while the DOE 2016 standard requires 98.60%. A 0.60% improvement may seem small, but consider that losses under test conditions decrease from 1,500W to 1,050W. The 450W savings represent a 30% decrease in transformer losses, and the total energy saved per year (8,760 hours) is 3,942 kWh.

ENERGY STAR Program: Product Labels

The ENERGY STAR program was created by the US Environmental Protection Agency in 1992, and it has been widely successful. The following are some of its achievements:

  • ENERGY STAR has helped homes and businesses save over 5 trillion kilowatt-hours and $450 billion in energy expenses, avoiding 4 billion metric tons of CO2 emissions.
  • The program ROI has been remarkable: for every $1 invested by the US EPA, homes and businesses have invested $250 and saved $350.
  • The environmental ROI is also considerable: every $1 invested by the EPA has achieved 3 metric tons of greenhouse gas reductions.
  • The program has also been marketed successfully: 90% of US households recognize the ENERGY STAR logo, and labeled products have been used in 97% of homes.

The US EPA has created performance criteria for each product category, and only those that are tested successfully get the label. You can check the specific criteria for each category on the ENERGY STAR website, including:

Applications Product Categories
Heating and Cooling Air-Source Heat Pumps


Central Air Conditioner

Ductless Heating & Cooling


Geothermal Heat Pumps

Room Air Conditioner

Smart Thermostats

Ventilation Fans

Appliances Air Purifiers (Cleaners)

Clothes Dryers

Clothes Washers





Water Heaters Heat Pump Water Heaters

High Efficiency Gas Storage Water Heaters

Solar Water Heaters

Whole Home Tankless Gas Water Heaters

Lighting Ceiling Fans

Decorative Light Strings

Light Bulbs

Light Fixtures

Building Products Residential Windows, Doors and Skylights

Roof Products

Seal and Insulate

Storm Windows

Office Equipment Computers

Imaging Equipment


Voice over Internet Protocol (VoIP) Phones

Electronics Audio/Video

Digital Media Player

Set-top Boxes

Slates and Tablets



Other Products Electric Vehicle Chargers

Pool Pumps

Smart Home Energy Management Systems

Water Coolers

The program has labeled over 75 product categories and around 75,000 specific models, and the average home saves around $450/year after upgrading to ENERGY STAR. To make sure you get the highest-performing appliances and equipment available, you can review the annual ENERGY STAR Most Efficient list.

The main benefit of the ENERGY STAR logo is simplifying your appliance and equipment purchases. Instead of having to review complex specifications for multiple products, you can simply focus on labeled options: these have been tested successfully according to US EPA requirements.