Today I propose to answer a question that you probably ask yourself if you are looking for a heat pump to replace your fossil or electric heating? Indeed you certainly want to calculate the consumption of your future heat pump and know if it will be profitable or not. Then you wonder how long it will run per day.
On the other hand, if you are thinking of buying an air to water heat pump, you may have some hesitation about where to place your outdoor unit in the garden and would prefer to know first how long it will be on during the day in order to decide on the best location.
In this article, we will review how the heat pump works, discuss the key factors that influence how long a heat pump runs during the day, and give some tips on how to optimize that daily run time.
How long does a heat pump run per day? On average, a heat pump can run between 6 and 8 hours per day. However, this depends on a number of factors, including the size of the heat pump, the outside temperature, the insulation of the house and the energy needs of the household.
The operating principles of a heat pump
The different types of PAC
Before going any further, let's review the different types of heat pumps. Indeed, each of them is different and its daily operating time to vary to this extent. But they are all based on the same basic principle, which is the capture of calories in a "free" source of the environment, in order to transfer them to the medium that transports heat in the house.
The air-to-air heat pump
Otherwise known as reversible air conditioning, it captures the calories in the outside air thanks to an external group containing an evaporator and the necessary refrigerating circuit. These calories, hot or cold, are captured in the refrigerant which transports them to the condenser where a condensation (or evaporation in case of air conditioning) takes place. The calories are then restored on the air of the room. This type of heat pump is most commonly used as air conditioning in offices or at home, and to replace electric heating, because there is no need to install radiators.
The air water heat pump
The air-water heat pump is the most widespread because it is the easiest to install, and very popular in the case of a replacement of fossil fuel heating. It collects calories in the same way as its air-to-air cousin, in the outside air. Then it distributes it to the water in the home's heating system in the same way. Subject to numerous subsidies in most countries, it is the queen of the market today. It is ideal to replace the oil or gas boiler or the pure electric heating.
The geothermal heat pump
Somewhat more luxurious, because more expensive, the geothermal heat pump collects the calories in the ground via vertical or horizontal probes in which circulates an antifreeze fluid that establishes a heat exchange with the ground. Then the calories are returned to the water of the house. Perfect to replace fossil fuel heating systems, it also has significant benefits. But it is more complex to implement because of the drilling that must be done, which is not a benign operation for your garden. Its COP or coefficient of performance is one of the highest.
The water-to-water heat pump
Following the same principle as the previous model, it captures the calories in a water source such as a lake, a river, or a water table. As these natural elements are not easily available near a house, it is less widespread. However, it also has some advantages. Its COP is the highest, reaching 6 or 7, which allows it to show the best energy savings among all its cousins.
The refrigeration cycle
To understand the principle of the heat pump, it should be remembered that it is based on the refrigeration circuit which itself contains 4 essential elements:
The compressor Compresses the refrigerant, increasing its temperature and pressure.
The condenser The refrigerant is used to transfer the heat contained in the calories to the water or air in the house.
The regulator : Lowers the pressure and temperature of the refrigerant before it enters the evaporator
The evaporator Evaporation : allows to extract heat from the environment (air, water, ground) to transfer it to the fluid which then passes to the vapour state (evaporation being an endothermic reaction which consequently absorbs the heat of its environment, contrary to condensation which is exothermic)
What factors influence the running time of the heat pump during the day?
How long a heat pump runs per day is not a fixed figure that can be stated with certainty. It depends on too many factors, including the size of the heat pump, the outside temperature, the insulation and the needs of the household concerned.
The size of the heat pump
It's all about sizing in this case. A heat pump that is too small will run longer to reach the desired temperature. A heat pump that is too large will tend to run intermittently, turning on and off frequently, which can reduce its efficiency and life span. The right installer will be able to provide you with the perfect sizing.
The outside temperature
Of course, the heat pump runs longer in the winter than in mid-season or in the summer when it is not supposed to be running, except perhaps in mountainous regions. The colder it is, the harder the heat pump has to work to extract calories from the air and reach the desired temperature set point. And when it is warmer, it is the opposite.
Insulation of the house
A properly insulated house keeps the heat extracted from the environment longer, and therefore means that the heat pump runs less during the day.
Poor insulation, on the other hand, has the opposite effect, requiring the heat pump to produce new heat more often than not, leaving it running all day long without stopping, at maximum.
That's why we avoid installing heat pumps in thermal deprivations, except if you are an eco-offender and want to make money on the backs of not too attentive or informed customers. Which is not your case anymore now that you have read this article.
Energy needs of the household
If you are a couple without children, and you work all day, your energy needs are much lower than those of a couple with two children, where one of the parents stays at home to take care of the children. All the more so in the case where your heat pump provides domestic hot water. You must therefore take into account the habits of your family to get a good idea.
Heating only or Heating + Domestic Hot Water?
Your heat pump heating system also plays a big role. Indeed, if you have chosen to produce your domestic hot water directly via your heat pump, rather than with a thermodynamic tank or via a pure electric resistance system, then your heat pump will turn a little more each day in order to ensure the temperature of the DHW in the tank. Knowing also that it is necessary to periodically heat the domestic hot water tank (DHW) to more than 65°C in order to kill the bacteria that cause legionellosis. The heat pump will run between 10 and 15% more if you produce domestic hot water with it, compared to the option where you only provide heating. And if your family consumes a lot of hot water, this can go up.
Typically, below 800 meters of altitude we consider 2000 hours of operation per year in heating only, and 2300 hours in heating + hot water.
Setting the indoor temperature
Are you a great thrifty person and don't hesitate to pull out the sweater to get over a little 18-19°C in the living room? Then your heat pump will logically run for less time than that of a family that likes to have a good time with temperatures of 25°C and more in the living room! (We'll call them the eco-delinquents :)) It's the same logic in summer if your heat pump is used as an air conditioner, and you like to be cold like in the hotels of Dubai! Your heat pump will run much more.
In short, you have understood the logic. These 5 criteria are strongly dependent on your habits or needs, and have a great impact on the duration of operation of a heat pump during the day and therefore its electricity consumption.
How long does a heat pump run per day in detail?
Estimated average operating time of a heat pump
It is difficult to provide an estimate of this time, as it depends on your personal situation. But it is estimated that on average a heat pump runs 6-10 hours per day. This fits well with an estimate of 2000 hours of operation per year, if we consider that the heat pump runs during the 8 coldest months, about 8 hours per day. In fact: 8 * 30 *8 = 1920 hours, almost 2000 hours. If you make hot water, count a little more.
Here is a table according to the different cases: it is a rough and average estimate which is based on the hypothesis that we are in plain (altitude lower than 800m), and that we turn 8 months per year. From October to May.
|Heating only||Heating + Hot water|
|Less than 800m of altitude||2000 hours per year|
8h20 per day
|2300 hours per year|
9h30 per day
|More than 800m of altitude||2300 hours per year|
9h30 per day
|2500 hours per year|
10h30 per day
Of course in winter there is an upward variation in these estimates of how long a heat pump will run for a day. Whereas in mid-season, these estimates are a little bit too high. We take the average.
Autumn is spring
This period is called the mid-season, and the demand for heating or air conditioning is often lower, because of the milder temperatures. The heat pump operates for a shorter period of time, depending on the temperature requested by you.
Demand is at a maximum due to the harsher climate. Depending on your habits, the heat pump will run longer to meet your comfort requirements.
There is no question of heating, unless you live in a region worthy of Lake Baikal. But you still need hot water for comfort. So the heat pump runs a minimum, unless it works in heating only. In addition, you may have opted for a reversible heat pump that provides air conditioning, in which case it runs even in summer, more or less long depending on your set temperature in cold.
How can I optimize the running time of the heat pump so that it runs less during the day?
Let's take a brief look at the levers available to you to influence how long your heat pump runs during the day.
The right size of heat pump will avoid unpleasant surprises at multiple levels, whether in terms of power consumption, noise, and duration of operation during the day. Indeed, the right size allows you to have a heat pump that runs reasonably within 8 hours per day or less depending on your habits. But a heat pump that's too small will quickly satellite this value, degrade the equipment, and drain your wallet. Always ask your installer for a sizing report, and have it checked by an expert if you have any doubts.
Improve the insulation of the house
It goes without saying that a better insulation will allow you to install a smaller heat pump in the first place, therefore less expensive and less electricity consuming. On the other hand, your home will retain heat longer and reduce the operating time of the heat pump.
Using a programmable thermostat
For an optimal regulation of the indoor temperature, you can use a programmable thermostat, in order to indicate your living habits and not to make the heat pump turn for nothing. When you are not there, you can lower the room temperature automatically or remotely, and raise it 1 hour before your arrival for example. It is known, the home automation allows energy savings.
Maintenance of the CAP
Finally, regular maintenance, at least every two years, if not every year, will prevent the filters from clogging up and making the heat pump run longer for nothing. This will make it possible to control the fluid level, which if it is too low or if there is a leak, will mean that the heat pump will run longer per day to provide the same power.
After studying mechanical engineering, Julian entered the world of climate engineering in 2009. After having built his experience in the ventilationand then in the heating with the largest manufacturers of German origin, he became an entrepreneur in the renewable energies and in particular a specialist in heat pump and solar panels photovoltaic systems for thehabitat individual.