Swimming Pool Heat Pumps – The What And How

Hayward Heat PumpPool heat pumps are an increasingly popular method of warming a pool. They are eco friendly and have low operating expenses but there are some drawbacks.

What precisely is a Heat Pump?
A heat pump is a device for moving heat from one location to another. In the case of pool heat pumps heat is taken from the surrounding air and moved to the pool water. A heat pump can in addition be utilized to extract heat from pipes sunk into the ground as is usually the situation when a heat pump is used for a home heating system. The performance of air source heat pumps declines with the air temperature and ice formation is a problem at low temperatures.  
How do Heat Pumps work?
Refrigerators, freezers and air conditioning systems have been around a long time and although they are used for cooling they do operate in the same way. In fact the top-end swimming pool heat pumps usually incorporate a reverse mode in which they cool the pool.

A heat pump comprises a circuit containing a refrigerant that includes two heat exchangers and an electrically  powered compressor that pumps the refrigerant round. In the evaporator the liquid refrigerant evaporates at low pressure extracting heat from the air. The refrigerant, which is now a gas, is then pumped round to the condenser at high pressure where it condenses releasing heat into the water. The refrigerant then goes back to the evaporator to repeat the cycle.

When you are generating heat directly e.g. using gas, you cannot generate more energy than you put in (in practice it will be significantly less). Gas heaters are typically between 80% and 90% efficient. A heat pump, however, is different. Because it doesn’t produce heat, the heat energy produced is much larger that the electrical energy input. This means that even though electricity is a pricey power source a pool heat pump is still very much less costly to run than a gas pool heater.

How effective are Swimming pool Heat Pumps?
This is typically stated as their Coefficient Of Performance (or COP). This merely indicates how many times the energy output exceeds the energy input. For a residential swimming pool heat pump a value in excess of 5 is good. You must be careful, however, that stated COP values are comparable as they change with the temperature of both air and water. It is usually measured at 80 degrees for air and water however this is not a defined standard.

Pros and Cons of Pool Heat Pumps

  • Low running expenses
  • Eco Friendly
  • Zero emissions


  • More expensive to buy
  • Lower powered so takes longer to warm the pool
  • Cannot operate in very cold conditions

How to make a decision
If you wish the most cost-effective method to lengthen your swimming season and you heat the pool the majority of the time then a heat pump will be your ideal option. If you only want to warm your pool occasionally then you could be best with a gas heater for the reason that it will be able to heat the pool faster and its lower purchase cost should offset the larger operating cost.