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How to Survey a Heat Pump Outdoor Unit Location
A practical guide to measuring, photographing and recording a proposed heat-pump position.
- Last updated: September 2026
- Heat Loss Hub · For Installers
A heat pump outdoor-unit survey should record more than the space where the unit might stand. A useful survey should capture candidate location, available space, surrounding obstructions, airflow constraints, nearby openings, boundary and neighbour context, noise-assessment information, ground and mounting conditions, defrost-water drainage, service access, pipe route, electrical-route starting point, site exposure, photos and video, and any uncertainty.
The purpose is to create enough reliable site information for the proposed position to be assessed properly during design.
An outdoor-unit location is not just a rectangle large enough to fit the heat pump.
KEY TAKEAWAY
The survey records the proposed location and its constraints. The design determines whether the selected heat pump can be installed there.
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Send us the completed outdoor-unit survey alongside the wider project and we’ll assess the location as part of the full design.
What Information Should Be Recorded?
| Information | Why It Matters |
|---|---|
| Location reference | Keeps candidate positions traceable |
| Available dimensions | Shows how much physical space is available |
| Rear, front, side and overhead restrictions | Supports clearance and airflow assessment |
| Nearby openings | Supports product-specific siting checks |
| Boundary context | Supports planning and acoustic review |
| Neighbouring properties and openings | Supports noise assessment |
| Ground/base condition | Supports mounting design |
| Drainage | Supports defrost-water management |
| Service access | Supports maintenance and replacement |
| Pipe route | Shows connection practicality |
| Electrical route | Shows likely supply route |
| Photos/video | Provides evidence |
| Confidence | Separates confirmed information from assumptions |
Survey the space around the heat pump, not just the space where the heat pump will stand.
Use Candidate Locations
Do not assume that the first possible position is automatically the correct one. On some properties it may be useful to survey more than one candidate location.
For example: HP-LOC-01 — Rear elevation, HP-LOC-02 — Side elevation, HP-LOC-03 — Rear garden.
Each location can then be assessed later for available space, airflow, noise, drainage, service access, pipe route, electrical route, planning considerations and product-specific requirements.
KEY TAKEAWAY
A difficult property may need candidate locations, not one assumed location. This can be particularly useful where one position has a short pipe route but another has better acoustic or drainage conditions.
Survey the Location in Every Direction
A useful outdoor-unit survey looks beyond the footprint. The area around the proposed unit should be recorded from every direction.
Behind the Unit
Record wall, fence, nearby openings, pipe penetrations, surface condition and anything that may restrict the rear of the unit.
In Front of the Unit
Record what the heat pump would face — for example open garden, wall, fence, gate, path, door, steps, vegetation, another outdoor unit, or a narrow passage.
Survey what the heat pump faces as carefully as what sits behind it.
Left and Right
Record walls, fences, boundaries, structures, vegetation, access routes and other equipment.
Above
Look for windows, doors above, air vents, soffits, overhangs, roof edges and other openings.
Below
Record surface type, ground level, existing slab, paving, gravel, soil, drainage and standing-water risk.
Beyond the Unit
Record the wider site context, which may include neighbouring properties, relevant neighbouring windows, walls, fences, barriers, reflective surfaces and different building levels.
A close-up of the proposed location is not enough to show all of this.
Measure the Available Space
Record the physical space available around the proposed position. Useful measurements may include available width, available depth, available height, rear space, front space, left-hand space, right-hand space, overhead restrictions and access width.
Do not assume there is one universal clearance suitable for every heat pump. Manufacturer requirements vary by product.
KEY TAKEAWAY
Measure the available space first. Apply the selected manufacturer’s clearance requirements during design. The survey should record the site accurately enough for those requirements to be checked later.
Record Airflow Restrictions
Heat pumps need suitable airflow around the outdoor unit. The survey should therefore record anything that may affect the movement of air around the proposed position. Look for walls, fences, gates, sheds, vegetation, narrow passages, enclosures, opposing walls, corners and multiple outdoor units.
A location may appear physically large enough while still creating poor airflow conditions.
KEY TAKEAWAY
A space can be physically large enough for the heat pump and still be poor for airflow. The survey should record the restrictions rather than trying to make a generic judgement based on one clearance dimension.
Record Nearby Openings and Features
Nearby openings can become important once a particular heat-pump model and refrigerant are selected. Record the position of nearby windows, doors, air bricks, ventilation openings, drains, gullies, basement openings, lightwells and other relevant openings or equipment.
Do not apply a generic exclusion distance during the survey. The required distance may depend on the selected heat pump and its installation instructions.
KEY TAKEAWAY
The survey records the opening. The product-specific design determines whether its position is acceptable. This is particularly important where refrigerant-specific siting requirements apply.
Record Boundary and Neighbour Context
Record where the proposed heat pump sits in relation to property boundaries, neighbouring buildings, neighbouring windows, different floor levels, walls, fences, screens and other structures.
Measure relevant distances rather than relying on visual estimates. The boundary should be recorded as part of the site information, but it should not be treated as a universal pass-or-fail distance.
KEY TAKEAWAY
Boundary distance should be recorded, not used as a universal pass-or-fail rule. Planning and acoustic requirements should be checked separately against the applicable rules for the property and location.
Collect Noise-Assessment Information
Outdoor-unit location affects the noise assessment. The survey should therefore collect enough information for the acoustic assessment to be carried out later. Record where relevant: exact outdoor-unit position, neighbouring properties, relevant assessment positions, windows and other openings, distance to assessment positions, floor level, line of sight, walls or barriers, reflective surfaces, site photographs and wider property context.
Do not assume that the nearest neighbouring window is automatically the only position that matters.
KEY TAKEAWAY
Do not survey only the nearest neighbour. Record the information needed to identify the relevant noise assessment positions. The survey should collect the evidence. The actual noise assessment belongs to the technical design process.
Record Walls, Barriers and Reflective Surfaces
Walls and other structures around the proposed unit can be relevant for more than one reason. Record solid walls, fences, screens, building corners, courtyards, opposing walls and hard reflective surfaces.
A wall may potentially restrict airflow, act as a barrier, or affect the acoustic environment. The survey should simply record what is present.
KEY TAKEAWAY
A wall can be an obstruction, a barrier or a reflecting surface. Record what is there and let the technical assessment determine its effect.
Survey the Ground and Mounting Position
Record how and where the unit could potentially be supported. Possible situations include ground mounted, wall mounted, flat-roof mounted, existing slab, paving, soft ground and raised area.
Useful information includes surface material, level, condition, space, accessibility, existing base, wall construction where relevant, standing-water risk and flood exposure where relevant.
The survey does not need to specify the final plinth, bracket or fixing system.
KEY TAKEAWAY
The survey records what the unit would stand on. The installation design determines how it should be supported.
Survey Defrost Water and Drainage
A heat pump produces water during defrost operation. That water needs somewhere suitable to go. The survey should record surface beneath the unit, ground fall, nearby drains, gravel areas, possible soakaway area, paths, steps, doorways, gates, shared areas, public access, existing drainage, and areas where freezing water could create a hazard.
Also consider water already entering the area from roof runoff, downpipes, sloping paving and adjacent surfaces.
Do not survey the heat-pump position without surveying where the defrost water will go. A position may look ideal until drainage is considered.
KEY TAKEAWAY
A good drainage route should be visible in the survey, not invented later during installation.
Record Service and Replacement Access
A heat pump will need to be accessed after installation. The survey should therefore consider whether an engineer could safely reach and work around the unit. Check access to the location, working space, ability to remove service panels, gate widths, narrow passages, steps, access through neighbouring land, whether ladders or specialist access may be required, whether the unit could be removed in future, and whether a replacement unit could physically reach the same position.
KEY TAKEAWAY
A location that fits the heat pump but not the service engineer is not fully surveyed. This is particularly important for roof positions, side passages and enclosed rear gardens.
Record the Route Back Into the Property
The outdoor unit is only one part of the system. The survey should also establish how the unit could connect back into the property. Record the likely route:
Outdoor unit → External pipe route → Building entry point → Internal route → Plant area
Useful information may include approximate distance, entry point, wall thickness, changes in level, obstacles, external exposure, structural restrictions, access and existing services.
The survey does not need to size the pipework. It needs to show whether a practical route appears to exist.
KEY TAKEAWAY
The best outdoor-unit position can become the wrong position if the route back to the heating system is impractical.
For more detail:
Record the Electrical-Route Starting Point
The outdoor survey should also identify the likely electrical route. Record where possible potential isolator position, approximate route toward the consumer unit, external cable route, internal cable route, approximate distance, access restrictions and major obstacles.
Do not carry out the full electrical design here.
KEY TAKEAWAY
The outdoor survey identifies the route. The electrical survey determines what supply arrangement is required.
Record Environmental Exposure
Some proposed positions have additional environmental considerations. Record anything unusual such as strong wind exposure, coastal exposure, falling leaves, dense vegetation, snow accumulation, roof runoff, flood risk, standing water, debris and very exposed elevations.
These conditions may influence product selection or installation design.
KEY TAKEAWAY
Record unusual exposure conditions early so they can be considered during product selection and installation design.
Photos and Video
The outdoor-unit survey should include enough visual evidence for somebody who has not visited the property to understand the location. Useful photographs include whole property or elevation, proposed outdoor-unit position, view looking outward from the proposed position, rear, left, right, above, ground/base, drainage area, pipe entry point, neighbour context, nearby windows and doors, barriers and reflective surfaces.
One particularly useful photograph is the view from approximately where the outdoor unit would stand, looking in the direction the unit would face.
KEY TAKEAWAY
Photograph the location from the heat pump’s point of view as well as from the surveyor’s. Use video where the relationship between different areas is easier to explain by movement.
For detailed photo guidance:
Use Measurements, Not Visual Guesses
Important site information should be measured wherever reasonably possible. Examples include available width, available depth, distance to boundaries, distance to relevant openings, distance to barriers, access width, approximate pipe route and approximate distance to plant area.
“Looks far enough away” is not a survey measurement.
Where a measurement cannot be confirmed, record the uncertainty rather than inventing precision.
Confirmed, Inferred or Unknown
As with the rest of the heat-pump survey, it is useful to record how reliable the information is.
Confirmed
Measured or clearly observed.
Inferred
Strongly indicated but not fully confirmed.
Unknown
Cannot be established from the available evidence.
For example: Boundary position — confirmed. Underground drain route — inferred. Wall construction behind render — unknown.
KEY TAKEAWAY
An unknown should remain visible until somebody verifies it. This prevents uncertain survey information becoming an assumed design fact.
Example Outdoor-Unit Location Record
A completed location record might look like this:
| Field | Example |
|---|---|
| Reference | HP-LOC-01 |
| Position | Rear elevation |
| Mounting | Ground |
| Available width | 1800mm |
| Available depth | 1200mm |
| Rear | Brick wall |
| Front | Open garden |
| Left | Timber fence |
| Right | Open |
| Above | Kitchen window |
| Ground | Paving |
| Drainage | Gravel area approx. 1m right |
| Boundary | Measured |
| Neighbour receptors | Recorded separately |
| Primary entry | Utility wall |
| Plant route | Approx. 4.5m |
| Electrical route | Possible via utility |
| Service access | Good |
| Nearby openings | Recorded |
| Photos | Complete |
| Confidence | Confirmed |
The status should be: Candidate location recorded — technical assessment required
not: Heat pump location approved.
A survey should finish with evidence, not premature approval.
Comparing Candidate Locations
Where more than one possible position exists, record them separately. For example:
| Factor | HP-LOC-01 | HP-LOC-02 |
|---|---|---|
| Space | Good | Limited |
| Airflow | Good | Requires review |
| Noise context | Review required | Potentially better |
| Drainage | Straightforward | Difficult |
| Pipe route | Short | Long |
| Electrical route | Good | Good |
| Service access | Good | Limited |
| Planning | Review required | Review required |
The survey itself does not need to choose the winner.
KEY TAKEAWAY
The survey collects comparable evidence. The design chooses the location.
When Further Investigation Is Required
Some locations cannot be fully assessed from the first survey. Further information may be required where key dimensions are missing, noise-assessment information is incomplete, planning status is uncertain, nearby openings require product-specific review, mounting structure is uncertain, drainage cannot be established, pipe route is unclear, electrical route is unclear, service access appears restricted, or the candidate location depends on hidden information.
Possible survey statuses include: Ready for technical assessment, Additional survey information required, Noise assessment required, Planning check required, Product-specific check required, Further site investigation required, Alternative location required.
This makes the uncertainty visible rather than forcing an early yes-or-no decision.
Common Outdoor-Unit Survey Mistakes
Measuring Only the Unit Footprint
Problem: A heat pump needs more than enough floor area to physically stand in the position.
Better: Survey the surrounding space as well.
Assuming One Generic Clearance Fits Every Heat Pump
Problem: Manufacturer requirements vary.
Better: Measure the available space and apply the selected product requirements later.
Treating Boundary Distance as a Universal Pass-or-Fail Rule
Problem: Planning and acoustic requirements are more complex than a single boundary measurement.
Better: Record the boundary accurately and assess the applicable requirements separately.
Recording Only the Nearest Neighbour
Problem: The most relevant acoustic assessment position may not simply be the closest window.
Better: Record the wider neighbour context.
Ignoring Upper-Floor Windows
Problem: Different floor levels can affect the acoustic assessment.
Better: Photograph and record the full neighbouring elevation where relevant.
Missing Barriers and Reflective Surfaces
Problem: Walls and fences can influence the assessment.
Better: Record their position and construction where visible.
Forgetting Defrost Drainage
Problem: A suitable-looking position may cause problems once water and freezing conditions are considered.
Better: Record where the water can safely go.
Positioning Discharge Toward a Path or Doorway
Problem: The survey should record what is directly in front of the proposed unit.
Better: Photograph the view from the proposed unit position.
Ignoring Service Access
Problem: A unit still needs to be maintained after installation.
Better: Consider both installation and future service access.
Not Checking the Pipe Route
Problem: A good outdoor position can create an unnecessarily difficult route back to the heating system.
Better: Record the building entry point and likely route.
Ignoring Nearby Windows, Vents and Drains
Problem: These may become important once a specific product is chosen.
Better: Record the features now and assess them later against the product requirements.
Assuming One Location Is the Only Option
Problem: Some difficult properties benefit from comparing alternatives.
Better: Survey multiple candidate locations where appropriate.
Taking Only Close-Up Photographs
Problem: A close-up does not show the relationship between the proposed unit and the property.
Better: Take both context and detail images.
Approving the Location During the Survey
Problem: The site visit or remote survey should collect evidence. Product clearances, noise, planning and technical design still need to be checked.
Better: A proposed heat-pump position should be surveyed as part of the property, not as an isolated square of ground.
Outdoor-Unit Survey Completeness Check
Before completing the survey, confirm: candidate location referenced, available width recorded, available depth recorded, height/overhead restrictions recorded, rear recorded, front/discharge area recorded, left and right restrictions recorded, ground/base recorded, nearby openings recorded, boundary context recorded, neighbouring properties recorded, noise-assessment evidence captured, barriers recorded, reflective surfaces recorded, defrost drainage recorded, service access recorded, pipe route recorded, electrical-route starting point recorded, environmental exposure recorded where relevant, photos complete, video taken where useful, confidence recorded, and critical unknowns flagged.
The location can then be marked: Ready for technical assessment, or Further information required.
What Happens After the Outdoor-Unit Survey?
The survey creates the evidence needed for the technical assessment. The process may then look like this:
Candidate location surveyed → Product dimensions checked → Manufacturer clearances checked → Airflow requirements assessed → Noise assessment completed → Planning requirements checked → Product and refrigerant-specific siting requirements checked → Drainage and mounting solution confirmed → Pipe route assessed → Electrical route assessed → Location selected or alternative required
KEY TAKEAWAY
The survey establishes what is there. The design decides whether the proposed location works.
Frequently Asked Questions
Record the proposed position and everything around it. This normally includes available space, walls and fences, airflow restrictions, nearby windows and doors, boundary and neighbour context, ground/base, drainage, service access, pipe route, electrical route, photos, measurements and any uncertainty.
Measure the full available area around the proposed unit rather than only the unit footprint. Record rear, front, left, right and above. The selected manufacturer’s clearance requirements can then be checked against the surveyed space.
There is no single universal distance suitable for every model. Measure the available space and check it against the installation requirements of the selected heat pump.
Boundary position should be measured and recorded, but it should not be treated as a universal pass-or-fail distance. Planning and acoustic requirements need to be assessed for the actual property and location.
Not as a universal rule. Rules have changed over time and also differ between parts of the UK and different planning situations. The survey should record the actual boundary position and leave the planning assessment to the applicable current rules.
There is no single distance that guarantees acoustic compliance. The noise assessment considers factors including unit sound level, distance, assessment position, barriers, reflective surfaces and line of sight. The survey should collect the information needed for that assessment.
Useful survey information includes outdoor-unit position, relevant neighbouring properties, window positions, distances, floor levels, barriers, reflective surfaces, line of sight and site photographs.
The survey should collect the site measurements and evidence required for the acoustic assessment. The actual calculation should then be completed using the applicable MCS 020(a) methodology.
The correct solution depends on the property and installation. The survey should identify ground condition, surface fall, available drainage, gravel or soakaway areas, paths, steps, doorways, public/shared access and areas where ice could create a hazard.
Potentially, but the location needs to be assessed properly. Consider air discharge, defrost water, ice, service access, physical obstruction and product clearances. The path should therefore be clearly recorded during the survey.
Potentially. The window should be measured and recorded so product-specific, acoustic and installation requirements can be checked. Do not assume that every unit can be installed beneath every window.
Sometimes. The survey should carefully record width, walls, fences, airflow, discharge direction, access, neighbour context and service space. A narrow passage may physically fit a unit but still require further airflow or acoustic review.
Some heat pumps can be wall mounted where the product and structure allow it. The survey should record the wall construction, location and access. The final mounting solution should be determined during design.
In some circumstances, but roof-mounted positions require additional consideration including structure, access, planning, noise, vibration, drainage, wind exposure and future servicing. The survey should flag the roof position for detailed review.
Record nearby windows, doors, vents, air bricks, drains, gullies, basement openings and lightwells. These may become relevant once the exact heat-pump model is selected.
It can. Heat pumps using R290 may have manufacturer-specific requirements relating to surrounding openings and other features. The survey should record the site accurately and allow the selected manufacturer’s instructions to be applied during design.
This varies by model. The survey should record the physical working space available around the unit so manufacturer service-clearance requirements can be checked later.
Useful photographs include whole elevation, proposed unit position, view facing outward, rear, left, right, above, ground, drainage, building entry point, nearby openings, neighbour context and barriers.
Where more than one practical position exists, yes. Recording multiple candidate locations can allow the designer to compare noise, airflow, drainage, pipe route, service access, planning and product compatibility.
A homeowner can often provide useful measurements, photographs and video through a structured self-survey. Technical decisions such as final product siting, noise assessment, planning review and installation design should remain with the installer or designer.
Survey the Whole Location Before Selecting the Heat Pump
A useful outdoor-unit survey should record space, airflow constraints, nearby openings, boundary context, noise-assessment evidence, ground and mounting position, defrost drainage, service access, pipe route, electrical route, site exposure, photos and any uncertainty.
An outdoor-unit location is not just a rectangle large enough to fit the heat pump.
Survey the space around the heat pump, not just the space where the heat pump will stand.
The survey records the proposed location and its constraints. The design determines whether the selected heat pump can be installed there.
HEAT PUMP DESIGN SUPPORT
Send us the completed outdoor-unit survey alongside the wider project and we’ll assess the location as part of the full design.
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