Save oil and gas: are air conditioners good for heating?

Gas is to be saved, heat pumps cannot be obtained quickly, and firewood is scarce.

Save oil and gas: are air conditioners good for heating?

Gas is to be saved, heat pumps cannot be obtained quickly, and firewood is scarce. How about an air conditioner that warms the rooms? Why this makes only limited sense.

Anyone who thinks of an air conditioner in their own four walls should initially have one thing in mind: cool rooms, especially in high summer temperatures. But the systems can also heat on cold winter days.

Mono-split air conditioners are increasingly being discussed as a supplement to classic heating in uncertain times. Understandable - because not a few are worried about not being able to bear the high gas and oil costs in winter or even fear that the supply of energy sources will stop in the cold winter. But it is questionable whether the purchase is worthwhile.

The most important question first: How can you heat with an air conditioner?

"In principle, air conditioners are nothing more than heat pumps that work in the other direction," says Tim Gessler, editor of the trade journal "SBZ Sanitary. Heating. Air Conditioning". "A heat pump primarily heats, an air conditioner primarily cools. But the underlying principle is the same. That's why, if you reverse the refrigeration cycle, you can cool with a heat pump or heat with an air conditioner."

Most of these so-called mono-split air conditioners are small, permanently installed air-to-air heat pumps that consist of two parts: the cooling unit in the room and a compressor on the outside wall of the building. And they have a corresponding switching function, which means they can be used for heating. Depending on the equipment and technical requirements, this is possible at outside temperatures of down to minus 15 degrees, says Frank Ernst, Managing Director of the Building Climate Association.

Anyone who already has a split air conditioner can find out from the product description whether it is suitable for heating. Nevertheless, you still have to call in a specialist to determine whether the system has been installed in such a way that it runs trouble-free even at sub-zero temperatures.

By the way: The split systems should not be confused with mobile air conditioning systems, the so-called monoblock devices. These are usually cheaper, are often bought as a quick solution for cooling on hot summer days and are connected to the socket without installation. According to Ernst, however, they are not suitable for heating.

How expensive is the purchase?

The mono-split air conditioners are available from around 250 euros, plus installation costs. According to Alexander Lyssoudis from the Bavarian Chamber of Engineers, at least two trades are involved in the installation of buildings with external insulation - for a total of about two working days. He estimates the costs for this to be between 1500 and 2500 euros. "This is not a do-it-yourself solution," emphasizes Gessler.

It's also worth remembering that while split air conditioners don't use oil or gas, they do use electricity. Although some devices have the energy efficiency class A (very good) even in heating mode, the actual costs involved vary greatly in individual cases.

They depend on many different factors, such as the performance of the air conditioner, the period of use and the desired room temperature. The respective building also influences the electricity bill for heating, i.e. how good its thermal insulation is and how high the rooms are. Outside temperatures also play a role. Because the efficiency of the air conditioning system decreases the lower the outside temperature, according to Ernst.

So if you are thinking about having a split air conditioner installed, you should consult an expert beforehand to find out what electricity costs can be expected in each individual case. And don't forget: hot water is still a long way from being provided. A separate solution is needed here if you want to do without the existing oil or gas heating altogether.

The good news: There can be a government subsidy of up to 25 to 40 percent of the costs for the split devices if the models are in the list of eligible heat pumps from the Federal Office of Economics and Export Control (BAFA) (new subsidy rates from 15 August 2022).

Why can't I install the device myself?

Installation by a certified specialist company is required by law because of the refrigerants contained. In addition, the installation is complex and can have serious consequences if handled incorrectly, including for heating costs.

To connect the indoor and outdoor units, it is necessary to drill through the outer wall, the compressor is hung outside or installed standing. On the inside, the refrigerant line is routed to the indoor unit, which is often mounted on the ceiling. In addition, the device needs an external power connection.

A sticking point during installation: If the building has external insulation, this is also affected, according to Alexander Lyssoudis, who is a member of the board of the Bavarian Chamber of Engineers for Construction. The hole created during installation must be sealed tightly again, otherwise there is a risk that the insulating layer will become soaked with rainwater. "And then the insulation is ineffective."

One should also not forget: every room that is to be cooled or heated needs its own mono-split device. There are also multi-split devices in which an outdoor unit is connected to several indoor units. However, these are usually more expensive and the installation is considered to be more complex.

What can I do as a tenant?

Tenants need the consent of their landlord as soon as they intervene in the building fabric with installations and conversions. Otherwise you can make yourself liable for damages and be warned, according to Jutta Hartmann from the German Tenants' Association.

By the way: Owners of a condominium in an apartment building also need the approval of their homeowners’ association for the split air conditioning unit. However, Lyssoudis suspects that this decision will not always be easy to achieve. Because: "The noise pollution cannot be dismissed out of hand."

So these air conditioners are noisy?

Consumer advice centers advise paying attention to the decibel (dB) specification for the volume when buying a split air conditioner. The operating noise of the compressor and fan can be particularly annoying. But there are models whose external parts are no louder than 55 decibels. This corresponds roughly to the chirping of birds or a television set at room volume.

And there is another comfort factor: the system usually blows the heat from the ceiling into the room. "That means, of course, you have quite a recirculation of the air with dust turbulence," says Gessler.

Can split air conditioners really replace oil or gas heaters?

The Building Climate Association estimates that the devices already installed can provide a heating capacity of around 18 gigawatts. This would save around 2.75 billion cubic meters of natural gas. This helps with the goal of saving gas. But what you shouldn't forget: the electricity for operating the air conditioning systems in this country is also partly produced from gas.

And if, for example, an entire residential complex with several apartments is to be heated with split air conditioning units in winter, according to Alexander Lyssoudis from the Bavarian Chamber of Engineers for Construction, it should be borne in mind that "certain power grids may then also be overloaded".

Whether it's a single-family house or an apartment building: Geßler, the editor, doesn't see the devices as a complete alternative to oil or gas heating. However, they can be useful if the rooms are also cooled with them in summer - and to leave the actual heating switched off longer in the transitional period. For Frank Ernst from the Building Climate Association, too, the air conditioning systems in winter are one thing above all: a supplement to the heating system.

In the end, the question arises as to whether you really want to accept the costs for purchase and installation - and the rising electricity costs for operating the system.

(This article was first published on Thursday, August 11, 2022.)

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