When choosing home appliances, consumers prefer energy-saving ones. When it comes to the energy efficiency of air-source heat pumps/Heating And Cooling heat pump, people often stick to Grade 1.
Many believe that buying a Grade 1 air-source heat pump will save electricity, and they avoid Grade 2 and Grade 3 models.
But do you really need to be obsessed with the energy efficiency grade? Is Grade 1 really more energy-efficient? This article will analyze it for you.
What is the energy efficiency grade?
The energy efficiency grade is determined by the energy conversion efficiency, i.e., the Coefficient of Performance (COP) of the air-source heat pump. A higher COP means higher energy conversion efficiency and better energy saving.
Put simply, if two people run 50 kilometers, one only needs to eat 5 bowls of rice—each bowl supports him to run 10 kilometers; the other needs 10 bowls—each bowl only supports 5 kilometers. Obviously, the first person is more efficient and “saves rice.”
How is the energy efficiency grade of an air-source heat pump calculated?
The COP of an air-source heat pump/Heating And Cooling heat pump is calculated as: Heat output ÷ Heating power consumption.
In 2013, COP values for air-source heat pumps were divided into five grades, with the following correspondence:
- Grade 1: COP 3.4
- Grade 2: COP 3.2
- Grade 3: COP 3.0
- Grade 4: COP 2.8
- Grade 5: COP 2.6
You can calculate the COP by looking at the pump’s parameters, then determine the energy efficiency grade based on the COP value, product type, and heat output. For example, a normal-temperature air-source heat pump water heater with a heat output of 20,000 W and a power consumption of 4,340 W has a COP of 20,000 ÷ 4,340 = 4.608, which corresponds to Grade 1. Power consumption directly determines the amount of electricity used. For instance, two air-source heat pumps with power consumption of 2,000 W and 1,000 W will use 2 kWh and 1 kWh of electricity per hour, respectively.
Myth 1: Grade 1 energy efficiency is always more energy-saving.
As mentioned earlier, the energy efficiency grade is the ratio of heat output to power consumption; it is just a ratio and does not represent the actual power consumption of the air-source heat pump.
For example, two normal-temperature air-source heat pumps / Heating And Cooling heat pump have heat outputs of 10,100 W and 20,000 W, and power consumption of 2,680 W and 4,340 W, respectively. Their COP values are 3.76 and 4.6, corresponding to Grade 5 and Grade 1.
Although the second pump is more energy-efficient (Grade 1), their electricity costs differ: the 10,100 W pump uses 2.68 kWh per hour, while the 20,000 W pump uses 4.34 kWh per hour. The Grade 1 pump is actually more power-hungry.
Therefore, the energy efficiency grade does not truly indicate whether an air-source heat pumps / Heating And Cooling heat pump is energy-saving. The amount of electricity used ultimately depends on the pump’s power consumption. Judging energy saving solely by the energy efficiency grade is incorrect. As anyone who has studied math knows, with the same numerator, a smaller denominator gives a larger ratio; conversely, with the same denominator, a larger numerator gives a larger ratio. Thus, the energy efficiency grade is only meaningful (Grade 1 is more energy-efficient) when the power consumption or heating power is the same.
If both the numerator and denominator are different (as in the example above), the result may be unexpected. So when buying an air-source heat pump, do not rely on the energy efficiency grade to judge power consumption. A Grade 1 air-source heat pump is not necessarily more energy-saving than a Grade 3 one.
Myth 2: You must buy a Grade 1 air-source heat pump.
Many people prefer Grade 1 when purchasing air-source heat pumps. For example, two pumps with the same heat output of 20,000 W have power consumption of 4,340 W and 4,720 W, which are Grade 1 and Grade 3, respectively.
If it were you, you would probably choose the first one because it has lower power consumption (more energy-saving) and a Grade 1 rating (more efficient), right?
