Some people want to heat the water in their pool to enjoy swimming for longer but also their comfort. It is not uncommon to have or want to heat the pool in summer in some departments. The desired water temperature is different depending on the person, some are sufficient water at 20 ° as a swimmer, but most people will prefer water between 27 and 28 ° C. We will, therefore, take this temperature as the norm. I recall that it is possible to heat underground pools, but also above ground pools, the systems can be adapted to both types of pools.
There are different types of heating that we will cover in this article: the heat pump, the electric heater, the heat exchanger, and the solar collector. We will present the advantages and disadvantages of each of these systems.
The basic principles
To heat the water of a swimming pool, the energy supplied must be greater than the energy lost. When the outside air is cooler, the water continually loses heat. This loss of heat takes place at 90% via the surface, which is in direct contact with the outside air—about 50% by evaporation, 20% by convection, and 20% by radiation.
Effectively the movements of the water created by bathers or the wind contribute and increase the heat losses (a bit like a hot drink that one agitates). It is, therefore, necessary to limit the energy loss of the basin insulating it. For this, a simple bubble cover will significantly reduce heat loss by limiting evaporation. This tarpaulin is applied when nobody uses the pool (especially at night when temperatures are more relaxed).
Today, the quality of bubble sheets also reduces the effects of convection and radiation thanks to their insulating power, which allows them to limit the heat loss further. Some tarpaulins will even allow you to heat your pond by absorbing the heat of the sun and gaining extra degrees.
It is essential to know what the heating of your swimming pool can cost and to choose the heating mode according to this non-negligible criterion, especially since electricity rates have risen a lot in recent years—the price per kWh averages 0.144 euros (average between the different distributors).
How many kW does it take to raise the temperature of my pool?
To heat one m³ of water by 1 ° C, it takes 1,163 kW of energy (thermal), for a pool of 70 m³ we need 81.4 kW. So if you want to heat your pool water in one hour, you need a power of 81.4 kWh.
However, most products available on the market do not offer such power, and the cost would be substantial. But if you are less in a hurry, a lower power will suffice to satisfy you. Indeed, the speed at which you want to heat your pond will be critical in choosing the power of your heater.
For example, to heat a 10 ° C water from a pool of 70 m³ to 28 ° C, at the beginning of the bathing season, it will only take 18 hours with a heat pump of 81.4 kWh. But with a less powerful heat pump of 15 kWh, this pool would be heated in 98 hours, that is to say, four days. Attention, this data remains theoretical, because, in practice, it is necessary to take into account the loss of heat, which will never be wholly canceled even with good insulation. The outside temperature is different according to your locality; this criterion is also to be taken into account in the choice of the power of your heating.
The heating system must, therefore, increase the temperature of your pool but also maintain it throughout the use. The cooling of a few degrees is done mainly at night, in our example for a pool of 70 m³, a heat pump will suffice to maintain the temperature during the night.
The principle of a pool heat pump is to take energy from the air. It evaporates moisture in the air and then condenses it under pressure. This process gives off heat. The heat pump restores this “earned” heat to your pool water. The main advantage of a heat pump is its efficiency. It works with electricity, but it is much less energy-consuming than traditional heating.
Today, most heat pumps produce between 4 and five kWh per kW consumed (coefficient of performance COP = 4 to 5). This is four to five times better than a conventional electric heater that produces 1 kW of heat per 1 kW consumed (COP = 1).
In our case of a pool of 70 m³, a heat pump of 15 kWh will consume only 3 to 3.75 kWh of electricity.
Note that in the context of an installation of a heat pump, it is not necessary to undersize this one. Indeed, suppose that you have a heat pump of 8 kWh for a pool of 70 m³ of water: it would take you between 10 to 12 hours to increase the temperature of 1 ° C. This would be ineffective because the degree earned would already have been lost, the water would cool as quickly.
Compare heat pumps?
The performance of a heat pump is variable. They depend on the temperature of the water to be heated: the colder the water is relative to the ambient air, the pump will release the more heat. The outside temperature and the humidity of the air also have a significant influence on the operation of the pump. Indeed, the heat pump can draw much more heat from the moist air than from the dry air. The difference in efficiency, depending on weather conditions, can easily reach 30%.
So be careful when comparing heat pumps and their COP; look at the data with which tests were conducted, air temperature, hygrometry, and water temperature.
The electric heaters classic are an option for small pools, spas, or to complement solar panels. The advantage of these products is that they are much cheaper than a heat pump when purchased and are easy to install. But they are very energy-intensive since their coefficient of performance is 1. The power consumption of a pool heater is to take into account when installing this type of device.
On the other hand, the external elements do not influence the operation of the heater; when the temperatures are shallow, the heater will continue to produce the same energy.
The solar collectors are usually black in panels or spheres; they transmit the sun’s heat to the water circulating in the pipes. The energy thus collected is entirely free. Note that the efficiency to heat your pool water is often insufficient for pools of a specific volume. On the other hand, by associating it with another system, this one taking the relay when the sunshine is inadequate is the right solution.
Be careful of the space required to place your solar panels, which must often be placed on a roof and which involves the intervention of a professional.
The solar heating is much used for above ground pools, or you want to earn a few extra degrees the comfort of our swimming. So are no longer panels but often solar “domes.”
The heat exchanger: speed
The heat exchangers bring the heat from the central heating water to the pool water. Their power is higher than that of heat pumps. This is a benefit for users who want a fast heating mode. A heat exchanger of 60 kW will bring the water of your swimming pool of 70 m³ from 10 to 28 ° C in 24 hours. However, the energy consumption will be much higher.
The cost will, however, depend on the economy of the central heating: is it a gas or oil boiler or a combined system with solar energy? This economy will have to be taken into account.
Comparative swimming pool heating systems
|Pool heating energy||Pool heating type||Installation||Cost||A climb in temperature||Pool type|
|Solar heating||solar carpet;
solar cover/bubble cover;
|easy, no skill required except for the shelter||starting from $25||limited and dependent on sunshine||inground pool and above ground|
|Electric heating||electric pool heater||easy, no skill required||starting from $50||Heater function, thermostatic and autonomous||inground pool and above ground|
|From a boiler or a heat pump||heat exchanger||easy, minimum skills required||starting from $300||comfortable and fast||inground pool and above ground|
|Independent heating||heat pump||difficult, skills required or installation by a professional||Starting at $500||comfortable, fast and excellent performance||inground pool and above ground|