Heat pump location: why a garden installation can become expensive

Replacing a heating system with a heat pump is widely seen as essential to the energy transition. Grants, modern technology and quiet operation make it sound like a straightforward upgrade. Yet one factor is often overlooked: where the outdoor unit is installed affects not only noise and appearance, but also planning law, approvals and additional costs. A case in Stuttgart shows how a seemingly simple replacement can quickly turn into a minor administrative project.

The Stuttgart case: heat pump in the garden, bill from the authority

In Bad Cannstatt, a homeowner wanted to replace an old heat pump. The technical requirements were clear, and the new unit was meant to go where the previous one had stood: at the back of the garden, on the owner’s own plot. To many people, that sounds routine. Then the planning authority got in touch.

The authority requested extensive documentation, including site plans, extracts from the land register and precise details of the unit’s position on the plot. According to the owner, the cost came to around €1,600 for paperwork and planning alone. The heat pump itself had not even been installed at that point.

The location of the heat pump can cost more than the technology itself if it is outside the permitted area.

At first glance, the case may appear to be a local annoyance. In reality, it reflects a fundamental principle of German planning law that can apply virtually anywhere, whether in Stuttgart, Cologne or a village in Upper Franconia.

Permit-exempt does not mean: “Put the heat pump wherever you want”

Many people hear the reassuring statement that a heat pump is “permit-exempt”. This is true in many German federal states, but it merely means that a conventional building permit is not required. The underlying planning rules do not disappear as a result.

The development plan, which every local authority sets for certain areas, plays a central role. Among other things, it defines:

• the so-called building envelope, meaning the developable part of the plot
• distances from the property boundary
• permitted ancillary structures in the garden

Small technical installations such as heat pumps can often be dealt with relatively easily when they are located inside the building envelope. However, if the outdoor unit stands freely in the garden outside this area, the legal provisions come into play - often alongside a substantial set of additional documents.

Why a garden location can become a cost trap for a heat pump

When planning a heat pump, homeowners usually focus on the level of grant support, noise output, efficiency rating or delivery time. Its position in the garden, by contrast, can seem like a minor point to settle quickly with the installer. That is precisely where the trap can lie.

Typical “problem locations” include:

• standing freely in the middle of a lawn, far from the house
• directly beside the terrace to keep the façade visually clear
• close to the property boundary to reduce pipe runs
• on embankments or small retaining walls

These locations are often outside the defined building envelope. Once that is the case, many authorities want full details: where will the unit stand? How large is it? Does it still count as construction under the relevant regulations, or is it classed as an ancillary structure? Each question can lead to plans, fees and delays.

The issue is rarely the heat pump itself, but the attempt to hide it “inconspicuously” somewhere in the garden.

What homeowners should clarify before buying

Anyone wishing to avoid problems with the authority should work through several points early on, before the heat pump has been ordered and an installation date arranged.

Check the development plan: where is the building envelope?

The first step is to obtain the development plan. It is often available online through the local authority’s geoportal or on request from the planning department. The key details are:

• the marked developable area of the plot
• notes on ancillary structures in the garden
• rules on separation distances and noise

If the proposed location for the outdoor unit lies entirely within the building envelope, the likelihood of extensive additional requirements is low. If the unit is moved to the far end of the plot or into a corner away from the house, the risk increases.

Contact the planning authority early

A brief phone call or email to the responsible authority can prevent a great deal of trouble. Useful questions include:

• Is an air-to-water heat pump permit-exempt in the relevant German federal state?
• Do the location and size matter?
• Is an informal sketch sufficient, or are official site plans required?

Anyone who resolves these points in advance can adapt the plan with their heating installer accordingly, rather than later being forced into an expensive alteration.

Noise protection and neighbours: the next potential garden conflict

Planning law is not the only issue affecting the location. Noise also plays a part. Heat pumps are considered comparatively quiet, but their continuous hum can become disruptive in peaceful residential areas, particularly at night.

Germany’s Technical Instructions on Noise Protection, known as TA Lärm, set limits that vary by area type, such as purely residential, mixed-use or village areas. State-level immission control law also applies.

Particularly sensitive factors include:

• the distance from a neighbour’s bedroom window
• sound reflections from walls, carports or glazed surfaces
• the operating mode at night, including night setback or silent mode

A “perfect” location for pipe runs can be the worst possible choice acoustically - and then the trouble comes not from the authority, but from the neighbour.

How homeowners can choose a suitable heat pump location

A good position for a heat pump outdoor unit meets three requirements at once: it is permitted under planning law, technically practical and acceptable to neighbours. Several practical guidelines can help when selecting a site.

Technology, law and neighbours: a quick guide to location

Aspect	What supports this option?	What should be considered?
Close to the external wall	Short pipe runs, often within the building envelope	Prevent sound transfer into the home and vibrations
In the rear garden area	Visually unobtrusive	Check whether it is outside the building envelope; pipe runs are longer
Near the property boundary	Occasionally practical for extensions	Noise protection, separation distances and planning-law compliance
On a plinth or frame	Protection from snow and improved airflow	May be more readily treated as a “structure” under planning law

Common planning mistakes - and how to avoid them

The same problems recur time and again in different towns and cities. Three classic examples are:

• “The installer will know all this”: Heating installers have strong technical knowledge, but planning law is often not their core area of expertise.
• “The old location must be fine”: Current rules may not have been considered when older systems were installed. New requirements can apply.
• “I can do whatever I want in my own garden”: This is exactly what the development plan restricts - often more strictly than many people expect.

Avoiding these misconceptions significantly reduces the risk of later alterations or a battle with paperwork.

Grants, costs and efficiency: why the location still matters

A carefully planned location saves not only stress but also money. Longer pipe runs mean higher material costs and greater energy losses. A hard-to-reach position makes servicing and repairs more complicated. If the unit later has to be relocated because of noise or legal breaches, homeowners may end up paying twice in the worst case.

Conversely, a location that has been properly agreed can even make grant applications easier. Some programmes require evidence that technical rules have been met, and in some cases that noise limits are being observed. Those who collect documents early and record their discussions with the authority are in a stronger position when questions arise.

Terms to know when choosing a heat pump location

Planning a heat pump location often involves technical terms that sound like administrative jargon but are easy to understand:

• Building envelope: The part of a plot where construction is generally permitted.
• Permit-exempt: No conventional building permit is required, but the general rules still apply.
• Separation distance area: The minimum distance between buildings or installations and the neighbouring boundary, usually governed by state building regulations.
• Outdoor unit: The part of the heat pump located outside that draws in air; it is often the reason for noise and location discussions.

Anyone who has a basic understanding of these terms will find conversations with planners, tradespeople and authorities much easier, without having to rely solely on instinct.