What is COP? – A Guide to understanding swimming pool heat pump efficiency

Like most people you want to get more out of your swimming pool investment and enjoy your pool for a longer swim period.  There are generally 3 options for heating a pool and the electric heat pump is the most common in Australia at the moment.

There are two limiting factors to a heat pumps output, 1 is the location of the heat pump and other is heat pumps ability to convert ambient air by way of performance into energy to heat the pool water.

The output or efficiency of the heater is known as COP or Co-efficient Output of Performance.

The COP is the ability of the heat pump to convert energy in to energy out for water heating.   The COP on any heat pump can vary depending on; unit design, the position / location of the heat pump and the heat pumps ability to source suitable air.

The COP is a sliding scale starting from 0.1 and going up from there.  The average COP we see in the pool industry in Australia is 4.0-5.5 in standard heat pumps and 7.5-16.1 when using Inverter heat pumps.  

The COP information is generally advertised as Summer Ratings, which doesn’t help when you want your pool heated for the cooler months.

Most heat pumps have a COP of at least 4.0. The higher the COP the less energy the heat pump will use to heat the water.

COP is often promoted as something that looks like this.

COP 5.5 – Ambient Air 26c Water Temp 27c Humidity 70%

The above simply means that for every single Kilowatt(KW) of energy in, the unit can produce 5.5KW of energy out when the outside air temp is 26 degrees.

So if a heater is advertised as a 11KW unit and the COP is showing as 5.5 the unit would use 2KW of energy per hour to heat the water.  i.e. 2.0KW x 5.5COP = 11KW

This is generally not helpful information if you want to heat your pool in winter and you live in Sydney.  The question you should be asking is what is the COP in winter?  It will typically look like this on a  brochure;

COP 4.5 – Ambient Air 15c Water Temp 27c Humidity 60%      

The test conditions for the rating of the COP will vary unit to unit, with many brands not mentioning their winter ratings for the simple reason that a 11KW summer rated unit is in fact a 7KW or 8KW winter rated heat pump.  

This information can be seen as misleading but it is generally more about getting the right size unit for the pool.