Energy efficiency ratio

A more efficient heating and cooling system can improve comfort and productivity in your workplace. To make the best choice, it’s essential to understand the key terms used in the heating and cooling industry. This knowledge will empower you to select the ideal unit tailored to your company’s needs.

The energy efficiency ratio (EER) measures the efficiency of the equipment that cools your building. This allows you to calculate the energy cost of cooling.

The EER is primarily used for cooling equipment, specifically air conditioners and heat pumps when they are in cooling mode. It measures the cooling output energy per hour divided by the input electrical energy.

“It compares the amount of cooling you’re putting out with the amount of energy you’re taking in,” explains Martin Thomas, Project Engineer at Natural Resources Canada’s CanmetENERGY Laboratory.

Natural Resources Canada has a searchable product list to help you find the most energy-efficient equipment.

How to calculate the energy efficiency ratio

The EER is calculated by dividing the energy removed from the cooling air, in units of BTUs, by the electrical energy consumed, in watt-hours, measured over the same period.

EER is measured at an outside air temperature of 35°C and an indoor air temperature of 26.7°C, with a relative humidity of 50%. Testing for the EER involves setting ambient air to that temperature in a climate chamber and then measuring how much cooling the device produces and how much electricity it consumes.

Energy efficiency ratio formula

For example, an air conditioning unit with an output of 10,000 BTUs and a power input of 800 watts would be calculated as follows:

What is a good energy efficiency ratio?

Thomas says EERs can vary from 6 to 19, with 8.5 considered adequate, “but the higher it is, the better the performance.” An EER of 12 is considered very good. A higher rating indicates that your air conditioner is more energy efficient, which is highly beneficial. An energy-efficient air conditioner reduces your utility bills and minimizes your carbon footprint.

Is the energy efficiency ratio a good measure?

“This rating is fine if you are comparing different heat pumps,” he says. “But they only test them at a specific condition and that doesn’t reflect how they perform for a range of temperatures.”

He points out that the EER is no longer the common way to measure cooling performance in heat pumps in Canada, although most manufacturers still print the value in their documents.

“It’s more of a means for comparing the different products. It’ll tell you which do quite well and which are not as good.”

Coefficient of performance is another standard measure

Manufacturers often quote the coefficient of performance (COP). It measures heating and cooling efficiency, and it is tested under varying conditions.

While the EER is used for cooling only and is typically measured at a fixed outdoor temperature, the COP tests heating and cooling equipment under varied conditions.

“It’s a more accurate reflection of how the equipment is used by the end-user and not just a test which rates the product at some arbitrary temperature,” says Thomas.

The COP score ranges from 1 to 5. A higher score equals higher efficiency and lower energy use.

Multiple COP tests at different conditions will give you a performance map for the heat pump, which can provide you with the energy use/cost over a whole year.

Electricity is more efficient than fuel when it comes to heating

Cooling and heating equipment that use electricity are more efficient than those that heat with gas or oil. 

“Because all of the electricity gets converted to heat, it’s 100% utilized. But with the process of combustion, you aren’t able to get all of the heat generated by burning the fuel into the air. You can never get 100% efficiency, or more, without heat pumping” says Thomas. He adds that, unlike electric heat pumps, thermally driven heat pumps can burn natural gas: “They are capable of getting COPs in the range of 0.80 to 1.30, depending on the outdoor temperature,” notes Thomas.

However, because electricity can be more expensive than natural gas in many provinces, it's important to consider time-of-use rates, subsidies, and rebates for installing energy-efficient equipment.

Consider the cost efficiency of the heating, ventilation, air-conditioning  appliance

While the EER or COP measures energy efficiency, cost is also an important factor to consider when installing heating, ventilation and air-conditioning (HVAC) appliances.

“The best-performing equipment is more expensive,” says Thomas. “So, there’s a cost-benefit analysis to consider.”

Investing in a high EER-rated air conditioner might not seem necessary for businesses that rarely use their cooling systems.

However, regardless of usage frequency, a high EER rating can lead to long-term savings on energy costs. Ultimately, the decision should be based on your specific cooling needs and usage patterns.

What are Canadian EER standards?

There are no minimum EER requirements for HVAC equipment in Canada, though a certification agency ensures that manufacturers properly conduct the EER test.

The ratings are displayed on the product label and are part of its specifications.

What is the seasonal energy efficiency ratio?

The seasonal energy efficiency ratio (SEER) measures the efficiency of air conditioning systems and heat pumps over an entire cooling season rather than simply under specific temperatures.

It is calculated by dividing the total cooling output (in BTUs) during the cooling season by the total energy consumed (in watt-hours) over that same period.

A higher SEER rating indicates greater energy efficiency, meaning the system provides more cooling for less energy consumed. This metric helps consumers compare the energy efficiency of different air conditioning systems, allowing them to make more informed choices.

“It’s a better metric to use for rating different HVAC appliances in Canada,” says Thomas.

The heating equivalent to the SEER for cooling is the heating seasonal performance factor (HSPF).  A higher HSPF indicates a greater energy efficiency when heating.

SEER and HSPF are particularly important in Canada, where hot summers and cold winters can significantly impact energy costs over time.

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