There are many efficiency standards that are being used across the world for assessing the efficiency of heat pumps. Here are the most common ones focusing on heat pump units made in the US and the EU –
Comparing The Efficiencies Of Different Heat Pump Units
CoP or Coefficient of Performance
The CoP is used worldwide for both heating and cooling. It's simply the heating or cooling output divided by the electricity input. It's not a good indicator of efficiency. However, it only gives a snapshot of how a unit should perform under very precise conditions. As the outside air temperature varies hourly and daily, this is not a good indicator of efficiency.
SCOP or Seasonal Coefficient of Performance
You'll see this in European units to measure the average heating efficiency. It's a much better indicator than the CoP. The manufacturer has to test the performance of their units at different outside air temperatures. The unit is expected to operate at a specified number of hours at each temperature per year, depending on location in Europe.
There are three zones: warm, average and cold. The heat supplied and electricity consumed for the specified operating hours at each temperature is accumulated and divided to give an average CoP for the year. The SCOP also considers the energy consumption for things such as standby mode. Typical SCOP values lie between 3.9 and 5.2 with a higher number meaning more efficient.
EER or Energy Efficiency Ratio
This is a measurement of the unit's cooling efficiency that's mostly used in the USA. It's a ratio of a unit's cooling capacity and BTUs divided by the watts consumed to produce it. This is only tested in one condition. Generally, 95 degrees Fahrenheit outside air temperature and inside return air temperature of 80 degrees Fahrenheit at 50 percent relative humidity. So it's not recommended to use this to estimate your annual energy consumption or assess how the unit will perform in your location; unless you live in a hot climate. However, it is rated between 11 and 16 with a higher the number, the more efficient it is.
SEER or Seasonal Energy Efficiency Ratio
It is used in both the US and the EU on units that operate in cooling mode. Manufacturers will calculate their units SEER value by testing it at several different outdoor temperatures to represent a cooling season. The units of measurement are different from EU models calculated on cooling per watts of electricity and US models calculated on BTUs of cooling per watts of electricity used in both cases. This is suitable for units installed in very average climates. It's a good way to compare different units. But not a good way to calculate the energy consumption unless you live in an area with pretty average weather conditions. Typically, you can find SEER values for US units between 14 and 24 and EU units between 5.25 and 7.2. The higher the number, the more efficient the unit is rated.
HSPF or Heating Seasonal Performance Factor
This is used in the US for the heating mode of air source heat pumps. It is the ratio between heat output in BTU's over a heating season divided by how many watt-hours of electricity we use to produce it. It also takes into account supplementary electric heating. Manufacturers calculate the unit's HSPF by testing at different temperatures to simulate a heating season. This is an estimate of how the unit will perform and it may not actually perform like this in reality, especially if the unit is oversized. It is a good way to compare different units. Typically, the value of a unit will be between 7.7 and 14 with a higher the number, the more efficient the unit is rated.
See the summary here in this infographic – Different Heat Pump Efficiency Standards – SEER, EER, HSPF, CoP & SCOP [Infographic]
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