Are heat pumps worth it for pools?

In 2026, Handyman Algarve quotes pool heat pumps in the Algarve as pool equipment: a unit near the plant room, fitted into the filtration circuit, that takes heat from the outside air and hands it to the pool water. Because it takes that heat from the air instead of turning electricity into all of it, it gives more heat than the electricity it draws, and its output falls as the air cools. Whether one is worth buying turns on four things: the months you swim, the cover, the spot and the electrical supply.

Inside the casing, a fan draws outside air across a cold coil, where the refrigerant takes heat from it; a compressor raises the refrigerant’s pressure and temperature; and a heat exchanger passes that heat to the water the filtration pump sends through. The electricity pays for the compressor and the fan, and the rest of the heat comes from the air, which leaves the fan colder than it arrived. Moisture in that air condenses on the cold coil and runs out of the unit, which is why it needs a drain.

It has nothing to add if the water is already as warm as you want it in every month you swim; it works against itself in a closed room or a tight corner, where it breathes its own cold air back in; and it needs the supply changed first where the electrical installation has no room for another load. In every case a cover comes first: every degree it keeps overnight is a degree no machine has to put back.

Is it a good idea to heat a swimming pool with a heat pump?

It is, when four things are true, and the case weakens with each one that fails:

• You want the water warmer than the sun alone keeps it. A heat pump adds the degrees the sun does not give, and with them swimming days. If the water is already as warm as you like in every month you swim, it has nothing to add; if you want to swim in spring and autumn, those are the months it has to be sized for.
• A cover goes on whenever nobody is swimming. Without one, the heat pump spends its electricity putting back what evaporation and the night took, and every degree lost is about 1.16 kWh of heat per cubic metre to make again (derived from NIST reference data, as the sizing section below shows).
• There is a spot for it. Outdoors, with the free air around it and in front of its fan that the maker’s instructions set, on a firm level base near the plant room, with a drain for its condensate, and away from bedroom windows, the neighbours’ included.
• The electrical supply can take it. A circuit that can carry it, and room in the house’s contracted power for everything that runs at the same time as the heat pump, the pool pump included.

In the 2021 census, 151,269 of the Algarve region’s 391,416 classic dwellings, 38.6%, were second homes or in seasonal use (INE, Censos 2021, quadro Q304). At a house used that way there is a fifth question: who switches the heat pump on. If it is off while the house is empty, each stay begins with a warm-up as long as the arithmetic below says, so whoever looks after the pool can start it ahead of the arrival, with the cover on to keep what it gives.

The air a heat pump draws on at Faro, month by month

A pool heat pump takes its heat from the air around it, so the air of the months it has to work in sets what it can give. At the Faro station (554, at the airport), IPMA’s climate normals for 1991 to 2020 give these mean daily air temperatures:

Month	Mean daily maximum	Mean daily minimum
April	20.7 °C	12.4 °C
May	23.5 °C	15.0 °C
June	26.8 °C	17.8 °C
July	29.4 °C	19.6 °C
August	29.2 °C	19.9 °C
September	26.4 °C	18.3 °C
October	23.3 °C	15.8 °C
November	19.6 °C	11.9 °C

These are air temperatures at one station, not water temperatures. A heat pump’s output falls as the air cools, so the same machine gives less in April and November, when the mean daily maximum at Faro is 20.7 and 19.6 °C, than in July, at 29.4 °C. At night the air falls towards the minimum: an uncovered pool gives more of its heat to it, and the heat pump draws more electricity for each kWh of heat it makes. A heat pump meant to add months either side of summer is therefore chosen on its output in the air of the coolest of those months, and a cover at night keeps what the warm hours gave.

The coast is not one climate, either. In the same normals, the warmest month’s mean maximum is 25.9 °C at Sagres, in August, and 30.5 °C at Vila Real de Santo António, in July, so the sum is made with the air where the pool is.

What size heat pump for a 40,000 litre pool?

Start from the heat the water needs. Heating water takes about 1.16 kWh per cubic metre for each degree Celsius at pool temperatures: that is the heat the water itself absorbs (derived from NIST reference data for water at 25 °C: 997.05 kg/m³ × 4.1813 kJ/(kg·K) ÷ 3,600), before any heat the pool loses and before the efficiency of whatever heats it. A 40,000-litre pool is 40 m³, so it needs about 46 kWh of heat for each degree (40 × 1.16), before losses.

That figure sets the scale, and five inputs turn it into a size:

1. The volume. Length times width times average depth, in metres, gives cubic metres; for a floor that slopes evenly from end to end, the average depth is the shallow end and the deep end added together and halved.
2. The degrees. From the water’s temperature when heating starts to the one you set on the controller. That temperature is your choice: each degree more takes about 1.16 kWh per cubic metre to reach, and a warmer pool loses its heat faster.
3. The time allowed. The heat needed divided by the hours you allow gives the output, in kW, the pool would need if it lost no heat; half the time needs twice the output.
4. The losses. While it heats, and every day after, the pool gives heat to the air through evaporation, wind and the cool of the night. The output has to cover them on top, and a cover on the water cuts them.
5. The air of the coolest month. Compare models on the heat output their datasheets give at the air temperature of the coolest month you want to swim in, and compare every model at the same air temperature, because the same machine shows a larger output in warmer air.

The best pool heat pump for a given pool is the one those five inputs point to, with its noise and the space it needs suited to the spot. No rule of thumb that turns cubic metres straight into kilowatts appears here, because such a rule fixes the volume and leaves out the other four.

How long does it take a heat pump to heat a pool?

Divide the heat the pool needs by the heat output the heat pump gives at that day’s air temperature, and the result is the number of hours it would take if the pool lost no heat at all. For the 40,000-litre pool above, the heat needed is about 46 kWh for each degree wanted; the output, in kW, is the datasheet’s figure for the air temperature of the day.

A real pool keeps losing heat while it warms, to evaporation, to the wind and at night, so it takes longer than that sum, and longer again in the cooler months, when the output is lower and the losses higher. A cover on the water while it warms keeps the difference smaller.

A heat pump fitted into the filtration circuit heats only the water the filtration pump sends through it, so the filtration runs for as long as it heats. At a house used for stays, the same sum, with the losses on top, says how far ahead of an arrival it has to be switched on.

How much does it cost to heat a pool?

Three numbers give it, and two of them come from your own pool and your own bill:

1. The heat needed. The volume in cubic metres, times about 1.16 kWh, times the degrees wanted, plus what the pool loses while it warms.
2. The heat pump’s ratio of heat given to electricity drawn, its coefficient of performance or COP, at the air temperature of the month, from its datasheet.
3. The price of a kWh on your electricity bill.

The heat needed divided by the COP gives the kWh of electricity; multiplied by your price, it gives the cost of that warm-up. Keeping the pool warm afterwards is the same sum, every day, for the heat it loses, which is where a cover pays its way. No figure appears here, because the volume, the degrees, the month and the tariff belong to one pool, and a number borrowed from another pool misleads.

What’s the cheapest way to heat my pool?

Keeping the heat the water already has. A cover on the water whenever nobody is swimming cuts evaporation and the heat lost at night, and the heat it keeps needs no electricity to make: for the 40,000-litre pool above, every degree it saves is about 46 kWh of heat that no machine has to put back. After the cover, what each way of adding heat costs to run follows from where it takes its heat:

	Where its heat comes from	What running it costs	What limits it
A cover on its own	It adds none: it keeps in the heat the water already has	No energy to make heat; only the handling, or a motor on an automatic cover	It can keep only what the sun has given
Solar collectors	The sun, through panels the pool water is pumped through	The filtration pump, running while the sun is on the panels	Least heat in the short days of winter, and none at night
A heat pump	The outside air, moved into the water by a compressor	Electricity for the compressor and the fan, less than the heat it gives	Its output falls as the air cools
An electric heater	The electricity itself, turned into heat	No more heat than the electricity it draws	The same heat in any weather, all of it paid as electricity

For each kWh of heat, a heat pump draws less electricity than an electric heater, and its COP at the air temperature of the day sets how much less. Which way costs least over a year for a particular pool also turns on what each costs to buy and fit, the space it takes and the months you swim, and a quote that prices each line lets them be set side by side.

A cover that keeps heat in is not, for that, a safety cover. A bubble cover is not a barrier and will not hold a person, so nobody walks on it, and no cover is a reason to leave children unsupervised. A pool with its cover partly on is the dangerous state, because the cover hides the water under it, and water ponding on top of any cover is removed, because a child can drown in a few centimetres of water.

Loulé’s building regulation asks that pools over 150 m³ that need heated water use solar collectors or equivalent technology where economically viable, plus thermal covers to limit heat and evaporation losses (Regulamento n.º 884/2024, Anexo 11, 4.3; read on 1 October 2026). Which technology counts as equivalent for a given pool is for Loulé’s câmara municipal to say.

What are the downsides of using a heat pump pool heater?

Each one has a mechanism, and each is worth weighing before a model is chosen:

• The price up front. The unit, and the work of fitting it: the base, the pipework into the filtration circuit and an electrical circuit, all paid before the first degree.
• An output that falls as the air cools. It gives least in the cooler months, which are the months a pool loses heat fastest, so a machine that looks ample in July can fall short in November.
• Noise. The fan and the compressor are heard while it runs, so it stands away from bedroom windows, the neighbours’ included.
• Air and space. It needs the free air around it that its maker’s instructions set. In a closed room or a tight corner it breathes its own cold air back in, and its output falls.
• Cold air and water. The air leaving the fan is colder than the air it took in, so it is not pointed at a terrace or a seat, and the water that condenses on its coil needs a drain.
• The electrical supply. A circuit that can carry it, and room in the contracted power for everything that runs at the same time.
• It works with the filtration. It heats only while the filtration pump sends water through it, so the filtration runs for as long as it heats, and the pump’s electricity counts too.
• Refrigerant repairs. Any repair that opens the refrigerant circuit needs a certified technician.

How much does it cost to install a heat pump in a pool?

It costs the sum of the lines of one job, and a complete quote writes each one down, so that two quotes can be compared line by line:

1. The unit, sized from the five inputs above, with the make, the model and its datasheet.
2. The spot and the base. Outdoors, with free air around it, on a firm level base near the plant room, with the condensate taken to a drain, and away from bedroom windows.
3. The pipework that connects it into the filtration circuit, where its maker’s instructions place it, over the distance from the spot to the plant room.
4. The electrical supply. The circuit from the board, its protection, and any change to the contracted power.
5. The first start. Water flowing through it, the controller set, and the condensate seen to drain.

In a building of flats, before the work it is worth reading the título constitutivo, the deed that sets up the horizontal property, and the regulamento, the condominium’s rules, and asking the administrator whether it needs the assembly’s authorisation.

A pool heat pump draws electricity whenever its compressor runs, so the circuit that feeds it and the contracted power of the house are checked before a model is chosen. The rule of ERSE, the energy regulator, is to choose the contracted power by what runs at the same time, not by the sum of everything installed: the heat pump counts alongside the pool pump, the oven and whatever else is on when it runs.

A household customer may ask to change the step at any time, but only up to the potência requisitada, the power the property was connected for, or the potência certificada, the power its installation is certified for, where that is lower (Regulamento de Relações Comerciais, Regulamento n.º 827/2023, article 69.º); below the maximum the installation admits, that is a request to the electricity supplier, and above it a power-increase request to E-REDES, the distribution operator (national rules, as read in 2026). The circuit and its protection at the board are an electrician’s work.

Monobloc or split: who fits it

A pool heat pump sold as a monobloc, all-in-one unit arrives with its refrigerant circuit complete from the factory. When it is fitted without opening or joining that circuit, the work is water and electrical work, and the Portuguese decree on fluorinated gases (Decreto-Lei n.º 145/2017) ties its certification duty to work that involves contact with the gas; any repair that opens the refrigerant circuit needs a certified technician. A split unit is different: joining its refrigerant pipes on site counts as installation under the EU F-gas Regulation (Regulation (EU) 2024/573), work for a certified technician and, for a customer, a certified company, and the Portuguese decree adds that the technician belongs to a certified company.

For a split, it is reasonable to ask for the technician’s and the company’s certificate numbers before work starts. These are the EU and Portuguese rules as read in 2026.

Looking after a pool heat pump safely

A homeowner’s part is the air around the unit and the drain below it; everything inside the casing is a technician’s. Before anything at the unit is touched, the power is off at the board and confirmed off:

1. Switch off the heat pump’s breaker at the board, and every breaker that serves it if it has more than one, or the main switch if the board does not label them, and check at that moment that it stops, if it was running, and that the lights on its controller go out. If it keeps running or its lights stay on, leave that breaker off and switch off the main switch as well. Where it has its own isolator switch beside it, switch that off too. Then press on at the controller: there should be no beep, no light and no movement. The controller’s off button only puts it on standby.
2. Tell anyone at home not to switch the power back on until you have finished: a unit that was running when the power was cut can start again by itself when the power returns.
3. Clear leaves and dirt from around it by hand, with gloves, and leave nothing standing against it. The coil fins are never touched: no hand, no brush and no pressure washer go over them, nothing is sprayed into the unit, and a hand never goes through the fan guard.
4. Look at where the condensate runs out, without opening any panel, and check that it reaches the drain. Water never goes onto the unit’s electrical parts.
5. Switch the power back on only when you have finished.

If the heat pump’s breaker trips, it is switched back on once only, and never with a smell of burning, smoke, scorch marks or water on the unit; if it trips again, it stays off and a technician looks at it. If the residual-current device, the diferencial on a Portuguese board, trips as the heat pump starts or runs, switch off the heat pump’s breaker first and only then re-arm the device, and the heat pump stays off until a technician has seen it. The unit is never pulled or turned to reach behind it, because its water pipes and its cable are connected to it, and any repair that opens its refrigerant circuit is certified work.

What to send for a quote

Photos and facts you can gather from the ground, with nothing electrical opened:

1. The pool’s length, width and average depth, or its volume if you know it.
2. The months you want to swim in, and whether the pool has a cover.
3. The spot where the heat pump could stand, photographed from the ground, with the rough distance to the plant room and to the nearest bedroom windows, the neighbours’ included.
4. The plant room, with the filter and the pump, as it is.
5. The electricity board, photographed as it is, with its door open if it has one and no cover taken off, and the contracted power from your electricity bill.
6. Whether the house is lived in all year, used for stays or let.

With that set, the quote comes back free, in English or Portuguese, with each line written out. The page on pool repair and maintenance in the Algarve sets out what the pool work covers and what sets its price.